Okay biggest nitpick: I really wish they explained why Morph and Bishop are on the team. Edit: I forgot they brought Morph back at the end of the last series.
Second Biggest: They slightly change the opening in the second episode to reflect Magneto on the team, but the end still has the old X-Men vvs Magneto clash.
That out of the way: The first episode is kinda Night of the Sentinels 2.0 It's been a year since Xavier's Death; no comment of him actually being in Space, just "gone" though I can understand the rest of the world thinking he's dead. FoH is using Sentinel tech to round up mutants, including Sunspot who sorta becomes the audience surrogate for this premier. We get introduced to the major players and the changes. Ends in an epic fight in a Sentinel Graveyard. Pretty much all the trailer footage comes from this episode.
The second episode is the better one of the two, which isn't to say the first episode is bad; just a standard good episode which is needed for those that didn't grow up/watch the old series. The plot, imo, really starts with this episode. Magneto is now head of the X-Men, though naturally the others are mostly chaffing at his being there. Though we get several really good scenes of Magneto in action, while tempering himself. This eventually leads to the Trial of Magneto where we really see the character stuff shine with Magneto expressing his desires and why he's doing this. While this is going on Jean goes into labor and has the best scene in the episode with Wolverine. Similationly We get an attack by X-cutioner, and I'm kinda surprised to see him this early on, which ends badly for one of the X-men and right when you think that is how the episode is gonna end; we get the real cliffhanger of another Jean showing up.
other points:
Magneto and Rogue apparently share a past? I don't recall that from the previous series, though I know from Comics she wasn't always on the side of angels; but I don't recal; the original series ever getting into that. Also, They maybe had a past relationship? I don't recall that from regular comics, but I do know they were a couple in AOA. Maybe they are hinting at that in case we get that down the line.
Rogue is the only one that bugs me, I know others have been recast; but she's the one that sounds... off to me... I'm also not fond of her hair design, too much white imo. Besides that, its rather amazing how faithful they try to be to the orginal series in not just design but animation, like even how they hang on location shots for setting feels right. They really are trying to make this feel like a natural "season 6".