Jointing Too loose/too tight

I'm sorry if this is a silly question, but I wanted to double check something. It's honestly in relation to a doll I have bought, but I've asked this question on normal DOA before, and haven't had much of a good answer. How can you tell if a doll is too tight or too loose? I thought that too tight dolls kicked and too loose dolls flopped, are there any other 'symptoms'?

Ok, now the doll I got has wings, which are strung with elastic. These appear to be part of the leg elastic, but were super horrible and hard to get on..... So although I think she needs a re string, I really, really don't want to... BUT she's such a beautiful doll that I want to pose her! I've tried sueding her, and it's defo improved her wing and arm posability, but she just can't stand! When standing, she will either fold up, or her ankle will collapse and down she goes
I'm also thinking her joint shape does not help - it is very a round peanut, and there are no locks, (not sure if that's the right word.) when she stands, her leg cannot lock into a straight leg, which is what I find helpful when posing other dolls.

Any advice would be greatly appreciated!