I was under the impression your typical phone charger, micro USB, power supply would be enough to support Xbox controllers (someone definitely correct me if I’m wrong here; my receiver’s in the mail).

WRT your concerns about keeping it on all the time; I’d suggest getting automated backups in place. Once you’ve finished configuring your environment to your liking, backup your SD card into an image. If your FS becomes corrupted this will be an easy install. It won’t cover all the progress that’s been made on your save games however. For this, I’ve created a step-by-step on how to setup automated nightly backups which will sync your save states with a google drive account. You can take a look, here:

Automate Nightly Backups of your RetroPie Saves by Syncing to Google Drive
byu/Laoracc inraspberry_pi

I’ve also put together a DIY for the RetroPie setup, here.