Der Kuenringer wrote on 2020-08-25, 14:27:

Or about the DIP switch settings on these - will they be the same across various models? The old IBM display adapters came with a warning that you could damage the monitor, if you feed them the wrong video/sync signals.

There is folklore that the IBM MDA monitor is not suitably protected agains too low(!) sync frequencies. A too low sync frequency could cause the line-output transformer to be overcharged during a line (technically correct term: saturated), which might blow the transformer or the horizontal output transistor. While TVs have an internal oscillator for the line frequency that is usually designed in a way that it can't oscillate too slow, the MDA monitor expects a properly timed pulse from the computer to terminate every single scan-line.

It is highly unlikely that you can damge (digital) multi-sync monitors, though.

Der Kuenringer wrote on 2020-08-25, 14:27:

Also, can someone explain to me why so many of these cards have zip-ties wrapped around their crystal clock oscillators?

A crystal oscillator has just 4 pins made of quite thin wire, and the steel can is quite heavy. Therefore, the oscillator might fall out of its socket quite easily during transport of the computer. The zip-tie is used to fasten the oscillator to the socket.

I don't know about using ET3000 with TTL monitors.
With VGA monitors, however, the rule is: if the card has the Sync ROM, it does support Hercules graphics on such monitors, the utility is VMODE.COM

This is a great question. I have some interest in getting an amber TTL monitor portable computer and switching the video for an early multi-mode SVGA so I can hook up external SVGA when at a desk.