Take a look at this thread:
https://discuss.grapheneos.org/d/16147-tips-for-a-new-user/18
MuchoMaas I have been trying to get as many FOSS versions of things as I can of late
It's even better to use services via websites than to install any apps at all. Example: Shazam.com will work without an account and better than any possible FOSS alternative.
MuchoMaas if there are any other tips from your own installation experience that might save me a headache or two I'd be most grateful
Read the whole install page. Pay special attention if host OS and host browser are in the compatibility list. Use a good quality usb cable.
MuchoMaas is are there apps that absolutely will not work without a google account
Not without a Google account, but without Google Play Services. Usually bank apps. Do a search in the forum for app compatibility. It's good practice anyway to put bank apps in a different profile, so that profile can have Play Services even if your main profile doesn't. I have PS Installed in my bank profile but it's not logged into a Google account, and no apps have yet complained.
As for the rest of your questions, hopefully someone else has the experience necessary to help you.