Sorry about the length, sometimes I get carried away with a theme, in a stream of consciousness text, typos and all.
In all music, I am more concerned with the audience than the players or sound guy since it is apparent in live gigs the only ones not considered is the audience. The band, roadies, monitor mixer and house mixer, all have their own tastes go by but no one actually consults with or goes out into the audience to see how it sounds or if the audience is even enjoying it.
In recording I always assumed that role of being the audience's representative in the session. It seems to have worked based on the records on the walls.

A factor seldom taken into consideration is that with higher power available for less per watt, speaker elements have grown less efficient because they have to be designed to handle more power.

There are a couple ways to make a dynamic element more able to withstand higher power. You can increase the voice coil wire size, which adds mass which lowers efficiency.

You can make a speaker able to handle further excursions of the diaphragm which presents a problem. The suspension of the cone needs to be more compliant, to be able to move to greater extremes. The means the concentrically of the voice coil in the pole piece(the magnet gap into which the VC is placed) worsens. At any given instant the position of the center axis of the VC and the pole piece is less known, with more variability. To solve the resulting rubbing that can result from less precise VC placement during it greater excursion, the gap is made wider. That decreases flux concentration which reduces driver efficiency a great deal deal.

The suspension can be made stiffer instead of increasing the pole piece gap. That also increases efficiency.

High power speakers, as a general rule, are less efficient than speakers of the same size that are designed for less power so more power is needed for the same acoustic power coupled to the room.
An array of small, efficient speakers in appropriate cabinet at any mid point frequency will create more acoustic power per watt.
But guitars are not signal generators operating at a single frequency. The speaker/amp/guitar combination is interested in specific parts of the spectrum, not the full audio spectrum. Speaker specs such as sensitivity are general clues but since they are taken at a specified very easy to produce frequency, usually 1khz or 400hz, the spec does not tell you as much as you might want to know in predicting how loud a particular combination of cab/driver/amp will sound like.
Flat frequency response is not a major goal in guitar amps so cabinet tuning is usually not done, which can greatly influence speaker efficiency as a system. But the tone difference between cabinets becomes pretty dramatic when a driver is working into an restricted infinite baffle style cab, like open back combo's usually are.
The question is, what efficiency do you get get in the portion of the spectrum your music requires to produce the tone you want? The specs on a spec sheet for a raw driver tells very little about that. Almost any speaker can be made to sound like any other but not at the same efficiency. Compare the flat linear response from a tight pole piece system in a horn, such as the Klipshorn or even the Altec folded midrange horns, and their great efficiency to your current 200watt blaster master driver. 1 watt, through most of the audible spectrum will drive you out of the house, 60 watts fills auditoriums. But 100 watts would burn up their highly efficient drivers.
Guitarists can get a closer approximation of their desired tone character from speaker experiments than anything they can do with their amps. The harmonic spectra generated by a speaker in appropriate cab or baffle can be very muscial, particularly with tube amps because of the lack of damping tube amps with little or no negative feedback have to control the fidelity of the cone movement to the signal level. Solid state amps, usually have a high damping factor so control the absolute fidelity of cone position to signal instantaneous level much better. That means less distortion generated by the cab alone. That is great for "reproducing" sound but less desired in "creating" sound. More attention needs to be payed to the amp signal impressed on the speaker in solid state because of that great control of the sound produced than with a tube amp.
A tube amp might sound good in a particular style of play but not in another because the amp and speaker are pretty much free agents doing as they please despite the intent of the other. As a result of that fact, solid state is more versatile and can handle a wider range of material, but needs to take more responsibility for the resulting sound. There is a lot more potential, but underused, upside potential in good SS designs. Given that the speaker is less a free agent, not imparting its character completely on the sound as much as tube gear allows, the player is freer to experiment with speaker/cab designs that have greater efficiency, without worrying too much that some mysterious mojo smoke might escape.
If you can create the transfer function of the sound you want, you can get it from a wider range of speaker choices and designs, but get it you will with solid state.
Players usually do not know that they are in control of the tone and are responsible in solid state. A high power amp, much more powerful than the speaker can handle is not a bad thing....unless a player treats the combo like a tube amp/speaker.
If they focus on tone, at a moderate lower SPL, the power section will simply provide the drive and not impart any particular sound character to the signal. In that way, the same tone can be had at various power levels. So why try to overpower the speakers when you already have the tone dialed in at 1/10 th the power? Maybe because they grew up with tube gear that did not sound the same at different power levels, and the sweet spot for a lot of desired tone was between 99 and 110% of amp capacity. They HAVE to run high power to get tone. A solid state user only overpowers their cab or gets close to clipping the power section due to misunderstanding their system.
The usual comment is thst "I need to get over the drummer". That is not an acoustic power problem, that is a personality problem. The audience is not going to be left in the dark as to whether you are playing or not dropping to YOUR rig's sweet spot which is any level well under clipping of the amp and within comfortable excursion limits of the speaker. In the very few situations where the guitar just did not stand out because of volume level, it becomes a problem for the house PA system to fill the need. Because you have 400 watts of SS power does not mean any person in the audience will enjoy it any better running at clipping. In fact, just the opposite is the case, all improves with lower stage volume...vocals, guitars playing, dynamic range of the whole group etc. If the band can't "balance" themselves, but instead run flat out in all instruments, it is boring and not musical.
If the drummer can't play as a member of a team, fire them, they have no business in a team. Play in your sweet spot, not the drummer's ego trip. A club with 200 audience does not need much power to fully fill their consciousness. Anything bigger has a PA system that is designed to do that. But to sound good, you much take responsibility for the overall sound, not just on stage but also in the hall so be prepared to fire the sound guy if they are playing ego trips with power, his job is to compliment your sound by re-enforcing it, not creating it. If you are not having at least 20 db headroom in the house system your music is dead and lifeless in dynamics, but most systems by dead ear sound guys are pushed to have 3 or less total DR between average and peaks levels. Take control, it is your career.

All this comes back to speakers. With solid state the choice and design or even power are not the major tone consideration it is with tube gear, if sensible levels are used that compliment your music.

This is from the perspective of a recording engineer, EE, gear designer and audience member, not a player.