Balance Transfer Card Questions

Hi! Please forgive me if this is a silly question, I’ve never done a balance transfer before. My main question is, when applying for a balance transfer card, is there any way to guarantee that the limit you receive will actually be enough to transfer the balance you need? I don’t want to hit the cardholder’s credit score with a hard credit check if we can’t actually make the transfer. If not, and if you do receive a lower limit, are you able to transfer just a portion of your existing balance (up to the limit you receive)? We have ~7.5k on an existing card and want to transfer it to a card with 0% interest for 18 or more months, because we will be able to pay it off within that time. The cardholder has an estimated 720 credit score (Experian). If possible we would love to also move 1.6K from a different card over as well, but that’s not as much of a priority. Cards I am considering are: Citi diamond preferred Citi double cash Citi simplicity Discover it cash back Discover it chrome I’m not sure how to choose between them, so any advice would be much appreciated. Thank you!