Last year the lines started at around 3-3:15pm for that 4pm entry and they did not let people in even one minute early. You will already be past the bag check but it's a zoo to get a wrist band once you go through the tapstyles. We showed up for a party that was not even close to a sell out and arrived at 3:30pm...…there were at least 250 people lined up across 4 lines at that time. By the time we had wristbands it was 4:20 and it was only that quick because my daughter basically cut in front of a large group that was busy arguing and didn't even notice they where next. It was like when the grocery store opens up an additional cash and several people are all looking at each other to see if anyone is going to make a break for it.....this timewe happened to be the ones who got there first.
They have changed the FP+ timing on the party tickets. You can certainly try to get 3 but most likely you will only get 2. There is no more time over lap so you have to finish the last one by 6:30 and your first one can't start before 3:45 so that doesn't give you 3 full hours.