Screen resolution and scan rates are paramount in these situations, as is the proper Video Adapter. IIfx couldn't get the 24AC I sent him to output anything but 640 x 480 x ???Hz until he got a new VGA adapter and now it's slinging screens at its max of 1024 x 768 x ???Hz so quickly that he's amazed.

There's nothing wrong with NuBus Cards (or PDS VidCards) & LCDs as long as the Cards output VGA at the required 60 Hz (considered flickery on CRTs back in the day) which is all many LCDs will accept. It's the NuBus & PDS Cards and the Macs that are limited the primitive FixedRes settings at odd (higher) scan rates of the ColorMacWorld of yesteryear that are problematic when it comes to using them with today's LCDs.

Some LCDs are "MultiScan" within certain ranges, while some refuse to work with anything but 60Hz.

Check the results I got with a few LCDs I tested in the IIsiColorPivotII_PDS_Card_HackProject™ thread.