Speaker height vs ceiling height

I really do not believe tall speakers are an issue. I have owned 8' tall electrostatic speakers and 6' tall dynamic speakers without any problems. Most of the really tall dynamic speakers place their drivers in a D'Appolito configuration, so the midrange and tweeters are not close to the ceiling anyway. Having the speaker near room bounderies (floor and ceiling) supports bass response and I seldom hear anyone complain about too much bass.

Yes, there can be too much bass, easily. In smaller room.

The size of the cabinet is not the issue; it is the position of the driver within the cabinet relative to the boundary that causes a concern.

Radiation patterns are effected by room boundaries. So radiation pattern should be considered when near ceiling etc. A dipole with figure 8 radiation would work quite well as would line arrays or horns designs.

I would think you want to avoid early reflections of ceiling similar to walls. Usually there is less distance to work with in regards to ceiling and floor than walls even.

I like to keep my speakers as low to the ground as possible but also with adequate elevation from floor. Having drivers as close to listening position elevation or slightly below is probably a good practice in general.

Tall line arrays might be a different story, but good ones that tall will cost a fortune.