Open can vary from steel-silverish to above platinum. Its incredibly diverse in terms of skill level, and really it doesn't matter whenever you get into open because like i said, it varies alot. You'll play against better players and become better yourself.
Also, ignore ESEA TF2 pugs. The pug system doesn't really work for TF2(somebody else can tell you why) and you only need a 1 week premium code if you're playing CSGO pugs or 10mans.
For tf2 pugs try inhouse pickup games, pug.na(if its even still alive) tf2mix, tf2center if you're new to the game, and i'm sure theres something else out there.
Best of luck, enjoy the game