In short, i'm a little concerned.
Take a deep breath, step off away from the edge...
You aren't the only one that has noticed dropped frames and a bit more UI jank on the S7 when compared to the 6P. I think XDA did a stress test to see how the S7 (SD820) handled heavy loads and if/how it throttled....Turns out it handled repeated benchmark runs like a beast and nary lowered a single score (GPU throttled a bit, but the new SoC went full tilt, full time). That being said, they did say that when the started looking at the overall UI performance, not under heavy load, but in those mundane, light duty day to day tasks that we are doing most of the time.... they noticed dropped frames, random stutters and skips and blink of an eye freezes in window transitions, etc. The S7, even with its more powerful internals, still isn't as smooth and fluid as the 6P.
But nothing is as smooth and fluid as the 6P.
It's just the nature of the beast. Samsung stuffs a whole lot of stuff on top of the base Android code, and all those new windows, UI modifications, there's a price to be paid. I'm sure I'll notice it when my wife's S7 comes in and I play around with it and give it a good once over.... but I won't care very much. It'll still be a fast phone and handle everything you throw at it without much fuss.