If these boots/gloves give bonuses to AC (e.g.,
Bracers of Defense), then they probably
should stack with Barbarian's Unarmored Defense. Just like Barbarian's UD can stack with use of a Shield.
If they set your AC to X (which would be very dumb; why would a pair of gauntlets set your entire body's AC, overriding e.g., Plate Armor?), then it shouldn't stack with Unarmored Defense or any other source for base AC.
Of course, BG3 probably shouldn't be giving out a ton of items that provide bonuses to AC, given 5e's bounded accuracy...
