I just wanted to add to what UltraMarknus had to say. I have a few different knock offs, and yes, the joints always seem to be loose. There are limited ways to try and tighten the joints, like tightening the screws at the joints. But with mine, tightening the screws does not tighten the joints as well as I would like, or to the level the HT True Types are. It might also depend on the specific figure or batch you get. But be prepared to have to possibly do the glue trick (drop some super glue in the joint and work the joint continually so the joint doesn't set but creates more friction) to get those joints tight. Personally, I'm ready to give up on the knock offs because they're a little more trouble than they're worth, and just stick with HT True Types at least for the more important figures. If it's for a background figure then the knock-offs are probably fine.
And ditto with what UM said about the wrists and neck.