If anyone is looking to try a 2 parks in 1 day adventure and cram in as much as possible, I’ll share my experience from 7/18.
In general, we walked at an average pace but consistently fell behind the pace of the TP schedule. I would not recommend just one day unless you have Express Pass (which we did through Royal Pacific) or really only care about 1/3 to 1/2 of the attractions. Even with Express, 2 full days is more comfortable if you want to do everything at a more casual pace.
8:00 - Enter Studios for Early Entry. Passed DM as it wasn’t quite open yet and headed to DA.
8:15 - Got in Gringotts line (posted 20 min). Walked around rest of DA until 9am.
9:00 - Checked app to see if Hagrid was open. Refreshed a few times to see all other IOA rides open with wait times except Hagrid. Not knowing when Hagrid would open, decided to do rest of Studios side. Skipped F&F based on all the bad reviews, did Mummy twice, grabbed a bite at Starbucks, then Transformers, Fallon, RRR, skipped DM since we had done it on a previous visit and not crazy about it, ET, Simpsons, MIB, and back around to Kings Cross around 12:45.
12:45 - Rode HE over to IA with the intention of getting in Hagrid line immediately (posted 180).
1:00 - Got in Hagrid line. Line did not extend out of entrance into Hogsmeade at all. Was actually able to walk a few minutes before reaching the back of the queue. Forecast was for storm around 3:45 so hoping to get through ride before that. Then posted time dropped to 120. No delays while I was in line and boarded around 2:20 for a low 80 min actual wait.
2:30 - Walked around in Hogsmeade for a few minutes, peeked into 3 Broomsticks but left as it was quite a line. Skipped Hippogriff and also skipped FJ (down for technical problems at the time).
3:10 - Left Hogsmeade and did JP Disc Center and JP ride.
3:40 - Meal at Thunder Falls Terrace. Storm started right on cue and we took our time eating waiting for downpour to let up.
4:30 - Clear skies rest of day, did Kong, skipped Toon Lagoon water rides, did Spiderman, Hulk, Cat in Hat, and Seuss Trolley with a little shopping time too.
6:30 - Left park to get rental car dropped off by 7:30 at Disney Car Care for start of WDW stay. Made it just in time.
We did minimal shopping, mostly just brief looking around in the ride exit shops, and no shows. We did mostly everything we wanted to, other than FJ being down and not having time to backtrack to it later, but at least had done it on a previous visit.
If you make a touring plan with Express Pass, the site may suggest a pretty ambitious schedule, and in our experience it was hard to keep that pace, even considering we were really lucky to get through Hagrid in a shorter time than expected. Extra minutes in Express queue, walking, and stopping to see something briefly all add up over the whole day and so many attractions. Inserting a few breaks and setting walking pace to slow as a worst case scenario may give a more realistic picture of what you can comfortably get through in a single day.
If I go back, I would do 2 parks 2 days for a more relaxed tour, but our one day worked out as well as we could have hoped.