Personally I only had an issue with my authenticator app that I used the time. Prior to installing Graphene, I kept the backup/sync disabled most of the time and only had it enabled for 24 hours and triggered a manual backup 2-5 times. That microsoft authenticator didn't sync regardless and I ended up locked-out for over a months from facebook, and took a while to regain access everything else.
Needless to say I don't use this app anymore and much prefer nfc / open source authenticators. I tried the same with google authenticator and manually synced only once and I had no issues. You might want to ensure double-check that your password recovery methods are up-to-date, just in case.
Unless you intend to keep everything in sync with your google account you might want to export your contacts, bookmarks and sms messages, and backup everything else. Exporting contacts and bookmarks are built-in into the apps, for the sms I used an app named sms backup & restore. I can't say it's the best backup app but I had no issues whatsoever. It also has an option to generate an html version of the sms, you might want to give that a try and review the amount of sms message that are currently on your device. Personally I was shocked at the quantity of spam message that were stored, and it made me change a few habits.
For my banking app I had to disable a few hardening options and it worked just fine.
I kinda like the more basic picture app in Graphene, but sometimes I miss the google version. Some open source camera app like open camera provides more options but I found it way overkill for my needs, and getting a good quality picture in various condition wasn't as intuitive for me.