I will say that I just returned from a quick trip to Universal Studios over Spring Break with DS. It was insanely crowded - which we expected being Spring Break. That said, I quickly realized that like our last trip (July 2017) we just weren't going to get through enough...I'm not a patient wait-in-liner ALL DAY. LOL
So we upgraded our passes to the VIP Tour Pass. Highly recommend!! Amazing experience!! But Insane price!!

haha
However, if it had been just me and husband, I think upgrading to the "exclusive" pass would've been perfect - which is why I mention it to you!
The Exclusive Upgrade can be done when you get to the park, so it gives you the flexibility to decide last minute. You have to decide quickly though, they sell out usually by noon! It gives you a one-time-front-of-the-line access to each attraction. Plus, there are some special sections for the shows, if you're interested. This upgrade was $79 or 89 dollars over Spring Break, which I imagine would be the same for July. Just a thought if you are only going to spend one day. Hope you have a fantastic time!!
As for
Disneyland, get the Disneyland App and pay for MaxPass. IMO, you will not regret it!

Enjoy! And let us know how the trip planning goes, etc!