If you're not interested in the shows (I don't think the RIP tour includes the water show), then I'd say Express might be the better option for you. Since it is only one night of HHN, you'll want to get there early (preferably in the park before it closes so you get an early start ahead of the people outside the gate). There's some people that use Express from the get-go and some people wait to use Express until the lines get longer (so they can revisit the first house(s) with Express later in the night). If you want to see all houses, scare zones, and possibly ride a few rides (your HHN Express Pass allows EP for each ride one time per night), but you don't want to be there late, I'd recommend the first option of using EPs straight-away. If you don't mind staying late and want to do a few houses twice, then the second option would probably be best.
Having said that, we don't know what the other show will be, so you might be interested when it is announced. But, you can still see it without a tour. I think the first show of the night can use EP, but I've never gone to the show that early in the night. With the RIP tour, you'll visit all 10 houses quicker than you can with EPs, then you can spend time in scare zones, rides, eat/drink, revisit houses in the standby line or call it an early night.
Both options have their pros and cons, and either option is much better than having neither. I see some people can Stay and Scream and only use standby lines and keep an eye on the wait times via the app and criss cross over the park and can do all 10 in one night, but that is very much not for me. My feet are worn out each HHN night and we just make a circle or two around the park hitting houses and zones as we go.
Hope this helps you some. I know it's a bit intimidating and confusing having not been before, but you'll have a great time. The scare actors, set designers, and make-up artists are all great at what they do.
