Ella, Xanthe and even Nico stated that it was artificial evolution for Clark and Alexis. Xanthe saying that his serum grants Evolution and hasn't failed. Nico saying she wants the same thing he gave those 2 and not the defective stuff he gave Klaus. Ella herself, saying they evolved mid fight. It's safe to assume that they reached lvl 5 via the serum like Ella did with the purple one she stole.
As for the Artificial Superhumans, that doesn't seem like it effects them much but they may not be able to get more expansive abilities. That's mostly speculation from me but with how evolution works for those who have monster parents, it seems like they give you knowledge and power as you evolve. Meanwhile, artificial superhumans, I assume, doesn't get any of that because the monster is most likely dead.
When it comes to who's artificial. That would be Klaus, Tiffany, and probably a lot of the agents in Hero. Probably not the original 5, mind you, but those with a lot of generic overlapping abilities. Everyone else, who recently joined Hero, seems to be natural superhumans. The others would be MC, Ella, Oscar, Danica, Deryl, Jake, Alice, Michael, Demi, and so on.
Overall, I don't think the artificial stuff really degrades them, too much, for both. Whether they became a superhuman via a monster corpse or evolved to higher lvls via a serum.