With the buy 2 days get the third free, I would do that if available, Not sure how you would work the park hopper into that??? You need the hopper or whatever it is called to do the Potter train other then that I wouldn't and have not gotten the hopper tickets.
Here it is.
https://www.universalorlando.com/Theme-Park-Tickets/General-Admission.aspx
$194.99 for adults for 3 days park to park and $184.99 for children. Think I would go that route. $50 a head more for park to park for 3 days.
I haven't looked at all the combos you could possible buy but there is enough at Universal to keep busy for 3 days if you have never been there or maybe even if you have been there???? I prefer when parks are open late and I can go back to my room in the afternoon, relax, eat dinner and hit the parks again into the night. All depends on the time of year (hours open) crowds etc. Mid July and you won't like 2-5 in the afternoon. The heat will take it right out of you. Cooler times of year is a different matter.
I don't want to ramble so....