Many of these topics have been discussed quite a hit on the forum. Have you searched the forum at all? It’s not the greatest search functionality, but you should be able to find a lot of answers to your questions via that method.
Some links:
https://forum.inaturalist.org/t/why-should-people-upload-pictures-of-common-species/7857
https://forum.inaturalist.org/t/how-often-to-observe-the-exact-same-plant-tree/35570
https://forum.inaturalist.org/t/how-often-to-make-observations-of-local-organisms/45536
https://forum.inaturalist.org/t/published-papers-that-use-inaturalist-data-wiki-3-2022-and-2023/34753
That being said, the main thing is that iNat should help you enjoy nature. Don’t feel pressured or overwhelmed. Make sure you’re having fun and only observe what you find interesting or enjoyable.