Is running on the Switch actually allowed? If so, how do I make sure it's running at 144fps? Sorry if I'm missing something obvious

No reason why you can't run on the switch. There was a "patch" made (for PC) for people who couldnt get it to 144fps to have that. I'm unsure how to get it to 144fps on switch tbh. There is a discord link with the devs and such. Maybe someone will know how in there.