I think a key is flexibility in pulling speakers out from the back wall. A lot of floorstanders will likely sound boomy in your room if you can only pull them a foot off the wall, but if you can pull them 4-5 feet out it becomes increasing unlikely they will overpower your room. Obviously things like bass traps can also greatly mitigate the effects of larger speakers in your room. I don’t know that any specific measurements will be helpful as every room is different, but putting a large tower that goes down to 20Hz would obviously be a potential problem although I know Micheal Fremer has his large Wilsons crammed into a relatively small room so again it can be very situation/design specific. And @onhwy61 brings up a very important point about being able to sit far away enough from the speakers so that the drivers have enough space to achieve coherency, but that is info you can probably get from the manufacturer if you become serious about a certain speaker. Sorry, I know this is mostly common sense stuff and probably doesn’t help you much so FWIW.
Along with SF I’d highly recommend hearing Joseph Audio, ProAc, Vandersteen, Usher, Von Schweikert, and Gershman if they’re at AXPONA. Rockport, Wilson, YG, Raidho, Estellon, MBL, Acora, and Vivid are always worth visiting. I think Boenicke and Wilson Benesch are very intriguing speakers that fly under the radar I’ve never gotten to hear so would absolutely hit those if they’re there. Nola, Spatial Audio, and Clayton Shaw’s Caladan speakers are some dipole designs that have always highly impressed me at shows as well. Just some ideas, and enjoy the show! Love to hear about any standouts (or disappointments) among the above or others if you care to share when you get back as I know you and I share common tastes in sound characteristics.