Tried scum, thought it was rubbish and glitchy, took me 45 mins to reach a friend who then killed me by accident.
Ark is pretty fun, has some really good elements like flying around on dinos, so fun but the pvp is lacking
Rust is great but a huge time sink with the servers wiping every month, it can be amazing fun meeting such random people yet has one of the most toxic communities i have ever seen in a game, the devs seem to be working hard to add more pve elements which hopefully will stop this toxicity a bit.
I will be buying fallout76 but not having it on steam and hearing about the bethesda launcher issues have put me off a bit.
Out of the above i reccommend rust over the others, i have 2k+ hours in it now nearly beating my time played on csgo and I dont intend on stopping anytime soon, they just added hot air balloons!