In my opinion, get the earliest time possible. It gives you the most flexibility to use your unlimited FOL privileges, which is best experienced without needing to stop to go do your tour; finish your tour early so you can move at your own pace until the park closes.
By far the best part of the night both times I’ve done RIP was when the tour itself was over and we were going straight to the front in every line for the rest of the night (remember, you use the RIP line all night, which means you even cut in front of Express), plus popping into the buffet for the occasional snack or drink. Give yourself ample time to experience that, because if I’m being honest, the tour itself is a tad overrated. You won’t learn anything new, and while the little extras you get (Candyman/Nope last year) are cool, they’re not like, mindblowing.