I'll be honest, we never plan for USO, other than "this is the day we'll do the wet rides" and "we'll do the HP stuff very early and very late". We are always offsite, no EP, and we always have a blast. That said, we go the 2nd week of June, when the parks are less hot and less crowded, and we plan for a minimum of 4 days in the parks, so we can adjust. We usually do rope drop to 2pm, and sometimes come back in the evenings to ride after the rain clears people out of the parks. We find the wait times to be reasonable this way.
That doesn't work for your dates or single day itinerary. That week of August will be hot and crowded. EP is your best bet to get the most out of the day. So it could be very much the same as your last experience if you go in thinking it's going to be another hot, long, crowded day. So try to change your expectations.
Get online or get some books and prioritize what you want to do and what you can skip. That way you can get on the things you really want to and anything else will be gravy. Pick a table service that ticks all your boxes so you can get out of the madness for late lunch. Consider getting a 3 park pass so you can spend a day at VB, leave late afternoon, eat, and go to the other parks that evening. You can't do it all in one day in August.
I like doing the IOA part of HP in the late evening (we go on arrival day evening), bc we've had very good luck with short lines in Hogsmeade at that time. We did Diagon Alley first thing at rope drop the first time we went over there, and did Gringotts first thing. Then you can browse the shops and get some butterbeer. Because everyone heads straight to HP, we had amazing luck in the Studios riding less popular rides with little to no wait in the first 2 hrs after open. We routinely rode Transformers, Mummy (2x even!), Simpsons and MIB in that first 2 hrs. Minions was never short enough for us to even get in line, and my kids don't do big coasters, so we didn't even try Hulk, or RRR. We generally waited 30-45 min for Spiderman in IOA, but with EP , it could be shorter. Shows are great for midday, and I would suggest doing a meal in CitiWalk or one of the table service restaurants. That's my take, ymmv.
The standard advice is to get EP, rope drop the big rides, use EP for the others during the busiest time of day, and try to do the rest of the big rides / areas in the last few hours.
I hope you have a good trip and find the Uni parks more enjoyable this time.
