Looks like they do have the option to put data onto a fictional memory card for the Psycho Mantis boss fight, so you can mix and match his comments however you see fit.
I picked up Metal Gear 1, 2, and Metal Gear Solid; MGS2 and 3 are the same as they were on the HD collection (which I have on Xbox 360), and the Master Collection versions take up a ton of space on the Switch from what I've seen, so I'm fine with just having the older games. (I've beaten The Twin Snakes several times, but I've never played the original Metal Gear Solid)
EDIT: I only played a bit of the game, but I like the inclusion of VR missions (they weren't in The Twin Snakes), and listening to the briefing, Colonel Campbell sounds more sinister and dismissive of Snake's post-retirement life, openly sneering at him. I don't remember him being like that in the Twin Snakes briefing; from what I recall (and what I've seem from skimming through a Youtube video of the Twin Snakes briefings), he was friendlier to Snake; I prefer that characterization. (also, Naomi Hunter has a British accent, though I think I prefer her without one; maybe that's just what I'm used to)