When in the "early Fall" are you going? HalloweenTime is a very popular time of the year (historically starts in early-September), so the weekends can be very busy. There are also Halloween Parties (starting towards the end of September historically) that impact
Disneyland's operating hours on Fridays.
Personally, I would make an effort to be at the parks at rope drop. The first few hours of the day tend to be least busy regardless of the day. I would tentatively consider starting in DL on Friday or Sunday because it does not have EMH/MM historically (EMH/MM impacts FL and TL), and then go to DCA on Saturday (no EMH historically). I don't have any specific time I'd recommend hopping; it's going to depend on what you want to do and how the lines are looking. I would definitely hop to DL after DCA closes (or vice-a-versa) and get in a little bit extra time at whichever park is open later.
I would download the official Disneyland App and you can use that to see what time the RSR FPs are for and then head over to the FP distribution location when it gets near to the time you want (I've found that the app runs a bit behind what is being distributed, so I'd head over
before the app says they're distributing the time you want).