Information is best obtained through the residency source listed above.
They can answer your questions directly regarding undergrad and give information on residency for the vet school (or direct you to the right person).
We live in TX but our son chose to go OOS undergrad and to vet school. The school was a better fit for him since he could never stand Texas A&M. Undergrad was actually cheaper with his scholarships and only needing 3 years undergrad where he went. Vet school is more expensive but he loves it there and luckily we could afford it. There are lots of variables to your first two questions and the school will be the source to ask. They don’t mind answering the questions. It isn’t easy to get residency but in TX not impossible. Where my son goes it is impossible. Whatever they are in year one they stay no matter what. So even though he has lived in KS for over 4 years he is not a resident. As far as best feeder schools. A&M is the highest feeder (obviously) other than that it is a big mix. In 2020 they accepted 155 in state residents and only 27 OOS. Didn’t seem to matter where the residents went undergrad just what their statistics were.