DraStic

Would in-game saves, (.sav files) work fine if transferred/used on a PC emulator or DS flashcart?

I need to know because I'm planning on getting the DS/3DS flashcart called, DSTWO PLUS; which plays and supports DS ROMs on any Nintendo DS system.

I'm asking this beforehand because I'm not sure if DraStic uses a different save file extension.

It depends on which direction you're going in and what kind of flashcard you're using. If you're using a .sav from a flashcard that uses a raw format (no header) it will probably work if you rename it. If it has a header it won't work. As for DraStic's .dsvs working on the flash card, I have no idea - it'll depend on whether or not they're raw and can ignore the DeSmuME footer.

Your best bet is just to use this website: https://shunyweb.info/convert.php