Even if I were to get the speed running widgets for twitch streams, I don’t have the material needed to stream directly from the console so I won’t be able to stream Mario kart speed runs unless I download an emulator for them. Of course emulators can be kind of sketchy as there are some games like Pokémon where official record speedruns have to be done on console.

Of course Mario Kart games have in game time, in both time trails and the Grand Prix, but Mario kart is one of those games where the in game time is always less than the official time. Though I feel like it should be okay since I’m not really shooting for world records. But would they be acceptable for submission? Even if I apply a picture or even a video, if the in game time is submitted, would they be mistaken as world record attempts?

Hey D4C, all Mario Karts have their own rulesets, so there's not a general rule on proof. As I can see you've submitted a run for MKDD, I'll quickly run it down for you:

RTA (Real Time) is required for submissions IGT (In Game Time) is preferred to add to your submission, but not necessarily mandatory.

For now, only top 10 times require video. There's no need to add any proof beforehand, though obviously, we always encourage adding a picture or video if possible.