With Hagrid's and VeliciCoaster open it takes the heat off the other HP rides and most especially in the morning.
Be aware that Hagrid's can go down at times (so can VeliciCoaster but Hagrid's more IME). We were just there and 2 out of the 3 mornings Hagrid's was down during Early Entry (one morning they had everyone leave the queue and closed it off) but we did ride it twice eventually, actually the morning that they had closed the queue completely by the time my husband had gotten done with VeliciCoaster the line was back open at Hagrid's which was about an hour later but it could also be an extended downtime. Just keep an eye out on the app.
Single rider was not open for VeliciCoaster on a Thursday or Friday, it was open on a Saturday for a while but had shut it back off towards the end of the evening. My husband def. got in faster with single rider at VeliciCoaster when it was open but he just did it the one time and it was technically just when the park had officially opened. He rode it on May 7th with a posted wait time of 45mins during Early Entry with single rider not being open in probably about 35mins, when he came out single rider was open so he rode it again and was back in line and completely done with the ride and back to me in 13 mins. I didn't check if the posted wait time had increased but I know it hadn't decreased. On the other hand on May 6th he was on VeliciCoaster just before 8am, wait time posted 15mins, went on it twice due to it being a walk on. So I'd say I'd do single rider if it was open if you notice the wait posted is long but your morning may be a better bet in general IF anyone in your party is willing to brave the coaster
My husband loved it, it's his fav ride overtaking Hulk but it's a no for me on it. I did do Hagrid's and it was a one and done for me but I did like that I could try it out once. Second time my husband rode it I just went with him in line and then right when they get to the loading spot I was placed on the side with the child swap area.
Our day without EP was a Thursday on May 5th and we didn't feel it was that bad but keep in mind my husband rode by himself a decent amount or he used single rider because I didn't ride most of the rides but his waits and the waits we did we didn't feel bad at all. It was a lot worse over at WDW for us in that respects.
If the one advice I can give is to utilize Early Entry. It's an hour long but even if you don't get there right when it starts you're going to be able to at least walk into the areas open and queue up if you want to or just be in there. I know for one morning in particular they let non-Early Entry guests in but held them back at Seuss Landing in a separate line. FJ and Gringotts consistently had very low waits (5-25/30mins) during Early Entry/right around park opening. If it were me I would have one morning focused on trying to get to Hagrid's IF your party is planning on doing it, then if successful do another morning focused on FJ and Gringotts.
If you look at High in the Sky's wait time just know that they only have 1 side running due to construction on the carousel.
For Early Entry when we went ONLY IOA was open. Both parks are open for Early Entry May Friday 27th- Tuesday the 31st (covers Memorial Day makes sense). But if you're going Thursday May 26th or earlier only IOA is open during Early Entry.
https://www.universalorlando.com/web/en/us/early-park-admission