I'll start by saying that you probably will want to see the show before seeing the movie, but it's not a must. Much of the humor is new content, but the running gags like Hawk rapidly aging, Wade not burning and guys pretending to have done all the work on their own trucks but only having installed new subs, etc. Won't be as funny if you're not clued in on the context. They do the "Previously on Real Bros" cold open that gives some context but you'll still feel a bit left in the dark at times. All three seasons are free on Jimmy's YouTube channel, by the way.
Jimmy, Wade, Nick and Tanner are still absolutely hilarious in their roles, as are most of the girls. (especially Lexy omg) I was sad that Pete Davdison and Victoria Justice didn't make returns, but there are a ton of celebrity appearances that make up for it. The story itself is pretty fascinating and the characters get into some really goofy situations. The social commentary is epic also. I'm still shocked at how entertaining and hilarious this was, and I'm already itching for new content from these guys. A proper 4th season would be great but a sequel to this movie would work also.