@Mouse . Good questions.
Silent instruments take the generic modern headphone jack (likely metric, but about 1/8 inch diameter). The over the ear type of headphone bangs on the bass side pegs, so I do not recommend them. A gamers type headphone for a single ear would be ideal.
You will not experience any intonation issues IF you keep the length of the string between the nut and the bridge exactly the same. An electric or acoustic instrument, it makes no difference. Not involving intonation but related to general sanity, also keep the bridge radius somewhat the same between instruments.
I have profound hearing loss and do not use headphones on my silent cello. It is likely do to having the strings right next to my ears.
I would start any amp on a low setting when turning it on with a cello attached, and slowly turn up knob a little at a time.
Take an old fashion spring type wooden clothes pin and secure to side of cello bridge, play a little, then whittle off ends of pin until you have adjusted sound level to taste.
I am of no help to you regarding video.
Without deviation from the norm, progress is not possible. —Frank Zappa
The future is already here—it’s just not very evenly distributed. —William Gibson