Taking 4 days after Oakhurst wedding--interested in missions, a beach day, history--less travelled spots but only short hikes
Monterey and Carmel fits your criteria. There are plenty of less explored, off the beaten path type hikes that you can visit locally. And, even in July, it won't be too hot. It will just be a bit expensive for the hotel, but that's going to be the case anywhere on the coast. Book accommodations soon.
I would say the Mission San Luis Obispo de Tolosa and then stay in Pismo Beach or Cayucos. They are two quieter, more off the beaten path, beach towns to the extent that is possible in CA.
Also a bunch of great vineyards in the area.
A bit further south is La Purisima Mission.