As of June 25: All of California’s national parks are open. Kind of. We can explain. (2020, June 16). Retrieved November 16, 2020, from https://www.latimes.com/travel/story/2020-06-16/all-california-national-parks-are-open-in-different-ways
Regarding covid and how open the national parks are there are now limitations on how the parks work and hours, they are open to prevent the spread of covid 19. Although a few of the California national parks are closed, a majority are open with certain public areas like the visitor centers closed. For an example of one of the national parks, Pinnacles National State Park, is partially open with limited parking and the east side still open.
I can speak from personal experience as to what these trails and campsites look like as for the fact that I was at Pinnacles National Park during one of the weekends of November this week. The public areas like the restrooms are mask mandatory places but in places like your campsite, you can have a mask off. In regards to hikes, most people distance and bring along their masks and try to distance themselves from the other hiking groups. I think that it is important for the national parks to maintain some profit to keep the preservation and systems open. There are also very high fire risks around various parks which are something to look out for regarding ecotourism in California specifically.