I know that a PSN Account is tied to the memory card which means if you wanted a NTSC (US) and PAL (UK, Aus) PSN Account you would need 2 memory cards.
With that said, in terms of trophies, can you sync trophies that were obtained from an NTSC game with a PAL PSN Account? Here's an example:
I have Atelier Totori Plus on my Australian PSN Account (PAL). If I were to get a NTSC copy of Ragnarok Oddysey and got its trophies, could I sync them to the same account as my PAL PSN Account or can I only sync it with the NTSC Account that I would use to get its DLC?
EDIT: I should note that in my example Ragnarok Oddysey is preferably a physical copy, not downloaded.
Best Answer
Yes, you can. I have a US copy of Mortal Kombat for the PSVita and its trophies sync with my PAL account just fine.
That said, it depends if you can play the game while signed in to your account, so with an NTSC Vita game played off a game card - it's possible, but since games downloaded are locked to a single account on the Vita, you won't be able to download an NTSC copy and play it while signed in to your PAL account.
Regarding the DLC you've mentioned - it's a different problem. You cant download DLC for NTSC games with a PAL account, nor you can play Vita DLC with an account other than the one owning it. So in your case, getting a US copy of Ragnarok Odyssey will lock you from playing and earning trophies for its DLC on your PAL account.