The 25 fps thing wasn’t meant to be taken literally… Regardless, you’ll have to optimize in ANY engine that you use or you’ll have another run of the mill poorly optimized “UE4 mod” for a game. UE isn’t perfect, by any means, but there are a lot of pros to it’s fidelity in other sectors of game design. If people get that fixated on something like having 20000 landscape layers, you probably need to rethink your creative process.
As for Maximum-Dev, that’s great and all, but at what expense did they achieve that? You’d have to examine the core rendering code between engines and see where they are optimized and where they cut corners. And again, did you read ANYTHING at all about how you’re technically only blending 3-4 layers at a time and not all 16?