If you want the authentic, full experience with the actual tag-team mechanics, you should use the RPCS3 Emulator on a PC to play the original PlayStation 3 version of the game.
What most players refer to as the "TTT2 PPSSPP file" is actually a mod of for the PSP. These mods replace the tekken tag tournament 2 ppsspp file download link
Unfortunately, it's not possible to download a Tekken Tag Tournament 2 PPSSPP file, as the game is not compatible with the PSP console, and therefore, not compatible with PPSSPP. If you want the authentic, full experience with