Your LSAT score and undergrad GPA matter very little for transferring between law schools. This is because law schools don't have to report the LSAT/undergrad GPAs of their new transfer students.
You know how when you're first applying to law school, your LSAT score and your undergrad GPA are basically all that matter? Well for transferring between law school: 1) your 1L GPA, 2) your class rank after your 1L year, and 3) your law school's place in the US News rankings, are basically all that matter. So the good news is that a lower LSAT or undergrad GPA won't hold you back. The bad news is that this puts a lot of pressure on your 1L performance, and you'll have to be right up at the top of your class in order to move into a T20 school. I've linked below what I think is a very a helpful blog post; the author gives some good stats and a couple prescient warnings about transferring. I'd especially stress his point about financial aid - it's personally the reason that I didn't pursue transferring up after my 1L year. That's not to dissuade you, rather just to make sure you're aware of the big potential costs of transferring.
https://blog.spiveyconsulting.com/trans ... tatistics/
Best of luck! Feel free to follow up below if you have any questions.