If you want to make changes, you make the changes in the profile and just reflash the module. I recommend deleting the profile and starting with default because you mentioned that it kept going back even after changes.
About the power button yes, that's the default behaviour on OP8, even I was surprised when I first got it lol, if you wanna change it, go to settings -> buttons and gestures -> long press power button. It's set to open Google assistant by default.
About the font I use the Google sans option it looks really good to me and is system wide. Xxx is great I've been using since my OP5 everything works like a charm. I don't really do statusbar tweaks but I'm sure someone else can help you with that
Cheers!
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Wasn't on mine, power button did what a power button should which is why I had no idea when I had unlocked the bootloader and flashed this, was weird.
I used to use this ROM on the 1+5 too. Since launch.
Great ROM