I'm a bit sheepish to admit that while I have owned a T3i for almost ten years I never actually used the video mode for anything but full-auto. I really didn't use the video mode full-time.

A few of you might recall that I do Youtube videos on the side whenever I can afford the time to shoot and edit but during Covid I saved my money and bought three new cameras to replace three dated and failing cameras which were becoming far too unreliable. Two Canon T3i's making up Camera 2 (Target) and Camera 3 (Overhead) and a Canon SL1 which is essentially a T4i for Camera 1 (Direct). Really nice and really fancy stuff but I've never worked with multiples at any given time.
I have two problems: One is that they all need to have a baseline brightness, ISO and white balance or you have to level them all out in editing and that's very time consuming. I've built a black/white card specifically for addressing this problem on my old cameras but they were a bit easier to set because white balance was pushbutton and brightness was done by manual iris control. I don't know how any of how that works on these cameras. A lot of the usual adjustments I make while in photo mode seem either stuck in auto or completely locked out.
The other is starting and stopping the recording process remotely. They don't need to be synchronized as a clapper and two minutes in editing aligns everything but the EOS series like other DSLR's have a 12 minute recording limit with no real timer, occasionally shorter when it decides to overrun the buffer and stop. The recommendation seems to use an IR remote but without any way to differentiate which camera you want to start/stop that's asking for problems. The regular wired remote jack seems to only function for focus and single frame shots and does not operate in video mode. Some say you need to use modified Magic Lantern firmware to enable this but I currently have no pressing reason to start hacking my firmware to add what I need, plus a pile of other features I don't even know how to use. Point is if I'm in the middle of a scene and a camera stops I don't want to unplug my mic, walk around the bench, restart the camera, walk back, plug in clap for sync and try to carry off where I was.