My son put in a regular application towards the end of December and switched it to EDII on 1/9 after we visited. We got an answer 3 days later…he got in. So, I would say they would look at switching after you visit as a good sign…you are taking EDII seriously enough to commit after you visit. The professors are great. I suggest scheduling a meeting with the chair of the department you are interested in so you can leave knowing for sure if you want to switch to EDII or not. We spent a full day there and really explored, including him doing an interview with a senior (schedule ahead of time), which gave him a wonderful student perspective. He did not get to take a class because they were on break, but that is the one thing I would have loved him to experience; however, we have no doubts in his choice. Good luck!
BTW, your stats are great. You should be a competitive applicant, but ED II will definitely make you that much more solid, as you never know with these highly selective schools. If you go to EDII, please go to the other ED post and post your stats for future applicants.
Go Gate!