So much to do in that area. I found the Lonely Planet Naples and Amalfi Coast guide, which also covers the islands near Naples and the Cilento region an hour to two hours to the south to be very useful.
Your interests sound to be more on the side of nature and perhaps less on the side of history and culture. The LP book - a bit of a pocket guide, but packed with many ideas, info, pics and details - is excellent.
We spent two nights in the Cilento and four nights in Naples, including day trips to Pompeii and the island of Ischia, which was great. See our TR at https://community.ricksteves.com/travel-forum/trip-reports/southern-italy-30-days-three-ways-to-travel
We got lots of ideas - more than we could do - from this forum. See https://community.ricksteves.com/travel-forum/italy/naples-and-environs-suggestions-per-favore
Acraven’s suggestions about Naples in that thread are worthy of consideration.
(Notwithstanding a different person’s suggestion that we go to Pompeii before the Archaeological Museum in Naples, our own circumstances led us to do the opposite and I was glad we had our introduction in the museum before being on-site with a guide. The RS audio guide for the museum worked beautifully, BTW.)
LATE ADDITION Just saw your other post. https://www.komoot.com/ Is another good app for hiking trail suggestions.