The speed of the high frame rate makes an already exciting game more exhilarating, comparable with the fantastic PC version. On Xbox Series X, Performance mode feels even smoother and more responsive than the already pristine Fidelity mode.
Fidelity kicks the resolution on both consoles up to native 4K while retaining that buttery smooth 60fps Performance, on the other hand, drops the resolution to 1080p but targets 120fps. Both modes feature improved shadows and lighting, which makes already beautiful stages like School and Venice Beach look even more impressive. THPS 1+2 on the new consoles offers two different display modes: Fidelity and Performance. It was hard for me to visualize what exactly developer Vicarious Visions could do aside from bumping up the resolution on the new generation of consoles, but after playing both the PS5 and Xbox Series X|S versions, it's clear the remake has some improvements that, while not drastic changes to the already incredible game, are undeniably impactful.
Update (March 25, 2020): Tony Hawk's Pro Skater 1+2 was a capable game on PS4 and Xbox One, running at variable resolutions while keeping that locked 60fps experience intact.