So i got a time on mario kart 8 deluxe, its not too good, but i want to submit it, only problem is i dont have any recording software to record my switch, is it neccesary to send a vid for the speedrun

99.9% of the times yes, you must have a video proof. Otherwise how would anyone else know you got it in a legit way?
If you don't have recording software, you can also (most of the time) record your run with your phone camera.
You can ask the game moderators to be sure.

From the rules of the game

[quote] Top 5 requires video proof. Best 3 cartridge submissions also require video proof.[/quote]