Having many apps will not affect battery life on Android in any meaningful way. Actively using them will. Apps can't just sit there and run in background, unless you explicitly gave them that permission.

Android also takes permissions away from apps after they haven't been used in a while anyway.

So most of the battery consumption will be from the apps that you actively need and use. Android's battery usage screen backs this up.

The metro app I installed when I was on a trip in Istanbul is still on my phone, but it's dormant. Yes, I should definitely uninstall it, but I really can't be bothered to do this all the time. On stock Android, phone takes care of this for me. On GrapheneOS, either I take that responsibility or face the consequences - which I don't really want.