Final thoughts - I'm posting because I think this thread will be a resource for future eclipses.
First, I have some prior experience photographing the Sun, specifically ISS transits. I realized a while back that my Thousand Oaks film filter forced me to use slow shutter speeds and/or high ISO. For transits, I decided to only use a 10 stop filter, being careful not to look through the viewfinder and only using live view. This way, I was only risking damage to my camera's sensor (which can be replaced) and not my eyesight. For the few transits I used this method, it worked and my sensor wasn't damaged. The settings used were just within the camera's limits: 1/8000, f/22, ISO100.
My original plan for the eclipse was:
Camera 1: Using an iOptron Sky Guider, shoot a timelapse with my 7D, 100-400, 2x tc, with solar filter.
Camera 2: 80D, Siggy 150-600, 1.4 tc, and solar filter for occasional shots. Also would use other lenses for non-solar shots, and would remove solar filter for totality.
Camera 3: T2i used for anything I might want to set up, such as maybe a fisheye.
Then, due to this thread, I realized something that has escaped me for a few years: The Thousand Oaks film that I was using lets in much less light than other safe options, specifically Baader film. After an internet search, I also realized that my film degrades the image IQ worse than the Baader. It was too late to upgrade my filters. I changed my plans:
Camera 1: T2i on guider with solar film. Based on the fact that I'm still new to the guider, I switched to a 1.4 tc with my 100-400, making the Sun's image a little smaller allowing for a little more drift in the frame before I had to adjust it.
Result: I haven't looked at all the frames (800+), but the guider worked relatively well. I had to adjust it 3 or 4 times.
Camera 2: 7D, 150-600, 2x tc, 10 stop ND filter for occasional shots. I planned to shoot 10 pre-totality and 10 post totality shots. Using live view to focus.
Results: These images look great. Sharp. My sensor does not appear to be damaged.
Camera 3: 80D. A few minutes before totality, switch the 150-600 (no filter) to this camera and shoot totality shots. After totality, put the lens back on the 7D.
Results: Great images of totality, although in the rush, I shot all of these at f/10 rather than my planned f/8.
Further results: I was moved by the awesome sight of totality. I didn't really care about getting more partial eclipse photos. After a few minutes of sitting in quiet reflection, I spent the rest of the time talking with the people around me - strangers at 12pm and friends at 2pm. I did allow the timelapse to continue. I believe the shutter died toward the end but this wouldn't be the result of solar shooting. It was just on it's last legs anyway.
Plans for future eclipses ( do I really have to wait 7 years?):
Upgrade Solar filters!
My camera for partial eclipse images will be on a tracker. Either I'll have another tracker or I'll ditch the timelapse. Adjusting the tripod for each shot is a chore. It would have been much more enjoyable If I had used my tracker for this.
For totality, I'll use a computer and have all shots automated. I knew this was possible for this eclipse, but didn't do it. Next time I will, so that the entire time of totality can be spent enjoying the event. I believe in this so strongly that I've already decided that if automation is not possible (for whatever reason), I won't even take photos. I'll just sit back and enjoy the insanely beautiful spectacle in front of me.