Nah Purrp was heavily influenced by 3 6 obviously, but he put his own spin on it and created a new sound. Songs like this:
are pretty unique and definitely distinguished from Memphis. A lot of the darker, more atmospheric trap shyt can be traced back to Purrp to an extent.
Plus in terms of style and fashion, Purrp brought in the whole street goth weirdo aesthetic. Obviously it made a big impact on A$AP, but low key a lot of newer Southern rappers were influenced by it. Basically everyone in Awful Records, dudes like Travis Scott, and even Young Thug to an extent. I mean, dudes like Thug probably weren't listening to Purrp, but what Purrp did, was he made it seem normal to be completely out there and like an alien in post 2010 rap. He proved you could be street, goth, and a ghetto rockstar-type figure all at once. That paved the way for newer rappers' personas to be accepted.
So without Purrp, the whole weirdo rap thing wouldn't have gotten as big as it did. Sure, you had other weird artists like Lil B and Odd Future, but in terms of acting like an alien, Purrp was taken more seriously than both of them, before he started beefing with everyone. A lot of people don't like weirdo rap, but the man really did push the boundaries in terms of how mysterious or eccentric a modern artist could be.
Oh and the whole comeback of 'trill' is almost entirely the direct result of Purrp and Raider Klan's initial run.