All of these parks will have plenty of people hiking and biking so safety shouldn’t be an issue, especially out in the county. No wildlife concerns; bears aren’t an issue here. Injury is always something to consider, if you slip in a stream crossing or whatever but again, should be plenty of people on these trails. I’d say it’s fine to hike alone, but for context I’m a 6’2” male so, grain of salt.

You’ll need to judge when to turn around based on fitness level but regardless, bring water and maybe even a clif bar or something. Maybe just go 20 mins out, and back on your first go. See how that feels, then you have a baseline and you can do 25 mins or whatever next time. Plus you know if you like that particular route or want to try something else. It’s ok to hike a short distance but it is not ok to realize you hiked too far out. But again, all these trails are beginner friendly.

Btw in this area it’s supposed to be bikers yield to hikers and both yield to horses. In reality a hiker not letting a mountain biker pass on a descent or a climb is a total dick move. Also don’t feel offended if a biker rings a bell- just trying to make sure you know they’re there. (Edited: fixed last paragraph)