Indeed. I ain't gonna lie, I try new molds all the time and buy too many discs hoping that some of them will be the magical disc that does what I want it to do every time. Fact is, though, discs that I buy for a specific shot rarely do what I want them to do. It's more about learning how to throw that shot than finding the magic disc that will hit that line every time, IME. With that said, though, the River kind of did feel like magic from the first few times I threw it and for sure go the farthest with the least amount of effort than anything I've experienced. Anything from laser straight to long turnovers are right in the wheelhouse of what that disc is made to do.
FWIW, I think the River is the exact right disc for the shot you're describing at your power level, especially a light GL. Once you work with them a while, you will dial them in, they'll become reliable for you and they'll never leave your bag. That's what happened for me anyway. I never play a round w/out a couple of Rivers in my bag. They don't click for some people, so there's a chance they won't for you, but give em a chance and you will likely be glad that you did.
The Underworld does sound interesting too. I'm with ya on that.