I need to confirm the validity with the moderators what I'll be using for a future run as the rules are very vague. At the moment, I'm playing FFVIII casually using Duckstation and would like to see if I can continue to use it for actual runs.

Is Duckstation a valid emulator for getting in the leaderboards? Would the category be "PSX Digital" if so?

I also read someone saying in one of the threads that WR will never apply to emulated games. Does this still hold true to this day?

Are there are other concerns that I should keep an eye on when using an emulator to do an actual run?

Hey, there is a complete guide to setting up Duckstation for speedrunning in the guides section: https://www.speedrun.com/ff8/guides/uh8r3

All the relevant settings required and some optional/preferences are included also.

Feel free to join the discord as that's a more convenient way to ask for help and advice also.

Good luck with learning!