Thanks for reaching out and welcome to the community!
100ms is a great target for IMAG, but that is rarely accomplished unless you have a very well designed (and usually expensive) system. I would say an acceptable amount of latency is 200ms or less in most situations. That would be 6 frames at 30 fps. I've found the average person doesn't notice or care until latency hits 300ms or more.
Ultimately, if you want the lowest possible latency for IMAG then you go with a studio camera designed specifically for broadcast. Nearly all cameras under $10,000 will have considerable latency on the outputs, even if they offer SDI output.
Budget and distance are going to be your biggest determining factors.
A bust shot (shoulders up) is going to take A TON of focal length to achieve from 85-100 feet away. That's roughly 2X the optical zoom that's need to get a medium shot (waist up). So if you have a 20X optical zoom that can get a waist up from that distance, then you would need a full 2X extender or 40X optical zoom just to get the bust shot from that same distance. This is going to be super difficult with most camcorders unless you find 4K camcorders that have a sensor crop feature while in HD mode - often called Clear Image Zoom (Sony) or Advanced Zoom (Panasonic and Canon).
If you go with legit studio broadcast camera bodies, then your lens options get much easier. However, they also get much more expensive. As an example - a 40X, 42X, or 55X (ENG or box) lens is basically what a corporate show or television broadcast would spec for a situation like yours. And those lenses alone will start around $50,000 and go up from there quickly.
Here are some focal lengths you will want to look for when searching for camcorders or lenses that can achieve a bust shot from 85' or more:
- 175mm minimum needed on any 1/3" camera sensor
- 225mm minimum needed on any 1/2" camera sensor
- 350mm minimum needed on any 2/3" camera sensor
- 450mm minimum needed on any 1" camera sensor
- 700mm minimum needed on any Micro Four Thirds camera sensor
What budget are you trying to work within?