Change default settings for data preview in background
I really hope that this is something the team is already working on, but just to make sure:
Please change the default-setting in Power Query for Data Load: Background data -> "Allow data preview to download in the background".
This should be DISABLED by default.
So many people are not even aware of how much unnecessary waiting time this default-settings can cause. At least this "performance"-stopper is avoidable in Power Query!