Yes, I think this is highly subjective, since it'll come down to your own size. Your height, arm length, hand size, and strength may all factor in, as it may depend on what level of leverage and reach you want, and what feels natural to you.
But yes, I would take the gauntlets into account, because if they bulk your hands up at all, you're probably going to want the grip to be large enough to comfortably accommodate that.
Personally, I find longswords to be the most comfortable around what we would call an "average" or "typical" size for them. Roughly 48" long overall, with about 36" of that in the blade. It gives you reach and leverage, but still remains within a size that can be used one-handed briefly.
A lot of the historical two-handed swords (German Zweihander, Italian Spadone, Iberian Montante) could typically be around 60" long, with a similar proportional blade/grip length within that. But these varied widely, and I don't think there's a "one size fits all" or "perfect" set of dimensions here. Some period examples might be closer to 70" in length, but that's pushing into the territory of "bearing swords", which were parade accessories, and not weapons. If you're going to use a weapon that's as tall as you are, or bigger, it might as well be a poleaxe.
