I think I promised to look into octoprint a really long time ago… Sorry, I got distracted and when I got back, I went to GRBL.
If you’re staying with the Marlin firmware, I think you’ve nailed the choices. If you can get octoprint to work, I think that’s the best option. Octopi is the easiest way to get started. I have an octopi, and some experience with it, if you get stuck. Webcam and timelapse is easy. The only possible gotchas are the temps and the gcode viewer won’t work (It ignores travel, I think). There might be some gcode that confuses it (G00 vs G0 or (comments) vs. ; comments). I bet most of that is just as compatible as Marlin. Also, the octoprint issue trackers are pretty good, so you can report problems with it there.
I switched to a GRBL controller built into the pi, and I don’t know if anyone else is doing that (and Ryan won’t be any help there, since he’s focused on Marlin for good reasons). With that setup, I run CNC.js, and I can do a little management. It’s a bit behind the octopi in terms of setup, etc. I did get a webcam working on the webpage, and I put in a request to the author to add hooks for starting and stopping timelapses, but I never tested his/her fix. I can load gcode files from my laptop, and if I set up the mpeg streaming, then I can see the USB video in the web interface. The web interface is my only way of jogging the machine under power.
Another important note is that CNC machines are more dangerous than printers (IMO), and they fail quite quickly. I doubt anyone would say it is “safe” to leave the machine alone. I’ve saved more than a few boards by being there when something went wrong. Then stopping the cut, or fixing a binding cable or something. There is also a fire risk, if chips build up, they can catch fire, although I think that’s sort of rare. I’ve left it running for little spurts during the cut though. Maybe instead focus on getting some hearing protection with builtin headphones and a good list of podcasts. 
You should also consider controlling the spindle power with something. That’s really nice to have, so it shuts up when it’s done.
Be sure to post what you end up doing.