Not sure what you're referring to as the "low" and "high" resolutions, but yes, palette-wise:
TGA 320x200/16-color = EGA 320x200/16-color
ETGA 640x200/16-color = EGA 640x200/16-color
Programmatically, they're different of course ("chunky" vs. bit-plane), and the Tandy ETGA video implementation doesn't support EGA's "higher-resolution," 640x350 graphics mode besides.
Great find with Eye of the Beholder, by-the-way. Dungeon crawlers tend to come across as dreary and tiresome to me, but it certainly does look and respond nicely on the RL, with rather decent Tandy and/or Ad Lib music and sound-effects to boot. As with Legend of Kyrandia, the Tandy music is more of a "chorused" version of the PC speaker soundtrack, but it comes across as unique and pleasant sounding, all-the-same.
I'd mentioned them on the Vintage Computer Forum, but Mindspan Technologies' "Face Off!" and "Joe Montana Football" are fairly impressive on the RL. Sports games aren't really my thing, but it's fun to load these up and just watch the computer play a game against itself. 😀