1) I have not been using an equalizer, just running banks in parallel. That was with the (27) 139Ah black Valence batteries I bought in 2014. They started life in an electric bus, then as an UPS in a printing factory, then I repurposed them. I am looking at equalizers now because I want to run these (4) green 138Ah batteries in series for a project.
2) Low temp has to be done with a temp probe connected to the BMS, which is always external as far as I know. I have seen videos that Will has done on this. You may want to check his Youtube channel.
3) By drift I mean that the 40Ah RT's and XP's will get below 12v. The RT's are only 2c batteries, but have low voltage cut-off. Also, their LED's will go from GREEN to YELLOW during low voltage. The XP's are 3c batteries, but do not have the cut-off.
As for the U27-12XP, I forgot to take one (older, black, 130Ah) out of my RV when I put it in storage last winter. The Genasun GV-10 Lithium MPPT Charge Controller draws a true .12mA max standby, and luckily the roof solar panel was in a dark building, so it did not try to charge. The Polar Vortex hit -27°F, and I was worried. When I was able to pull it out of storage, the battery was just fine, 13.05V! An equalizer draws 5mA, and that would have been a problem. As for leaving them in your cabin, I wouldn't unless you have to. I can't predict degradation, or what hungry rodents might do.
4) You need documentation and software for the Valence BMS to work, and cables. I don't have such. I just joined this site today, but noticed there is someone playing with this...search "Valence".
5) Yes, I met Ben at the Midwest Renewable Energy Association Fair in Custer WI last June. His EV truck caught my eye with all that beautiful green in the bed...same number of Valences that I bought 5 years ago. It was through him that I got connected with Muller Industries.
So, that is all I know. I think all your answers may be on this site.