I use BT cloud on a 2019 MacBook Air. I have ver. 126.96.36.199 of the BT Cloud extension. I frequently have to shut it down because it is using huge amounts of power even after it has beeen running for several hours and there has been little activty on the Mac. It's power demands make the Macbook Air run hot, so the fan is very load. When BT CLoud is shut down the Mac's fan starts to turn off shortly afterwards.
I do not use BT cloud for backup and I also have Google Drive, Box, Dropbox and 2 instances of Onedrive running at the same time. The other cloud storage apps use negligible power.