In a hobby it's easy to get carried away into doing things according to "best practices" when it's not really the point.
I've done a lot of redundant boilerplate stuff in my homelab, and I justify it by "learnding". It's mostly perfectionism I don't have time and energy for anymore.
If you're the only user and just want it working without much fuss, use a single db instance and forget about it. Less to maintain leads to better maintenance, if performance isn't more important.
It's fairly straightforward to migrate a db to a new postgres instance, so you're not shooting yourself in a future foot if you change your mind.
Use PGTune to get as much as you can out of it and adjust if circumstances change.