My phone is on 4G Volte all the time, it supposedly is capable of 5G but I have never seen it, others have. Not sure if that has something to do with my provider which is a budget one. I really don't care enough about 5G to figure that out. What I have heard is that some phones show 5G even when they are currently actually using 4G because there is no need for the bandwith, while sailfish OS only showd it when it is actually used.

Regarding battery life, I cant really tell how long it survives on idle. I never have that phone idling for that long. The most recent system update did improve power consumption though, by fixing some background process cpu waste. At medium use battery holds 2 days.