Looking for a RPG to play on PPSSPP

[mister seta 123]

Most of Ys games have been ported to PC, yeah.

Ys V is the only one without a remake, and I read that it is a shitty installment, so I think you should avoid that one for the moment.
Ys Seven was ported to PC by a Chinese company, and it hasn't been distributed with XSEED localization, but there are rumors about XSEED working on it right now. I suggest you to play it on PPSSPP if you can't wait, runs well and it's a great game, with one of the hardest final bosses in the series, imo. (I beat it on Hard. Can't imagine how would it be on nightmare!)
As for Ys IV/Celtea... it was released 1 year ago for PS Vita, so obviously it is not possible that they port that one for PC (or so I think), as it's a recent system. You can still play the first version, though Falcom wasn't involved as much on the two games of Ys IV, Mask of the Sun and The Dawn of Ys. Foliage Ocean in Celtea fuses the two of them, apparently.