Norman
Battery drain is worse in GOS. Where I could comfortably finish a day with 20-30% battery remaining, I now barely make it through a day.
No, this is because of how you chose to set up your device. You set it up in a way that's highly inefficient such as using Signal WebSocket push. You should check which active apps you have. If you have more active apps than sandboxed Google Play, that's why it's less efficient than the stock OS. Also consider using 4G (meaning 4G or below) or 4G-only mode if your 5G connections is inefficient.
I know this is not a fault of GOS, but notifications not working in most apps if you don't use (Sandboxed) Google Play services really sucks.
Many apps support other ways of doing it. It sounds like you aren't using sandboxed Google Play and are using inefficient push implementations instead which explains your poor battery life. You should use Molly's UnifiedPush with a MollySocket server rather than Signal WebSocket push. This will fix your battery life if it's what you've been doing.
Mobile network connectivity seems slightly worse, though I'm not sure if that's a fault of my provider (I have networking set to LTE+5G). Though LTE and 5G connectivity in my country should be more than excellent and have 100% outdoor coverage.
No, it's the same.
Multi-language support for the spellchecker is buggy and often doesn't seem to work. Even though I have two languages as my System Defaults, the spellchecker will seemingly always use the default language (English) and give me red lines when I type in my second language. This happens for both the default keyboard as well as for FUTO Keyboard (which I've also set up for multi-language).
It works the same as the stock OS at an OS level. You can use a different keyboard and spell checker.
Moving data between profiles without using a physical drive or the internet is impossible, which is sometimes really annoying. I know its for security reasons and maybe even impossible to implement. What would be really cool though is if you could designate a 'shared folder' between profiles somehow.
This is the same as the stock OS. It's easier to move data between a work profile or Private Space and the user they're within since they're integrated together more than user profiles meant to mimic separate devices.
Using NFC and turning it on/off through quick settings seems a bit buggy.
It should work fine.