The dvds and laserdiscs came from tapes, edited with a video toaster so I doubt that any of those are progressive, I assume that the LDs have extra picture information from a master that was both younger and less compressed on LD.
As for HD 4x3 masters, those were also created by the company in charge of the restoration alongside a 16x9 version, and is now somewhere in a vault within the bowels of Fox.
They started mastering in HD in season 5, but those are different masters than the ones used today.
And some parts of the series had to come from the original broadcast masters, hence a shift in quality.
This is also evident in the Twin Peaks bluray release, and TNG, but I bet you already knew this.
The best bet is DVDs, unless you have a hookup at fox and god forbid he has to deal with Rupert Murdoch’s merry band of attourneys, but at least the series isn’t owned by National Amusements.