I've actually had the exact opposite experience with the update.
Ever since getting my S7 in the fall, the lag and frame dropping was getting worse and worse, to the point I was thinking about just getting rid of the phone all together.
Since updating to Nougat earlier today, my phone's actually been awesome. After the update, it got SUPER hot and lagged up a lot as all of the apps updated and whatnot, but since then my phone has been performing better than it ever has.
It seems like the animations in general are better - allowing for more fluid - albeit slightly slower - transitions rather than transitions that were super fast in theory, but always seemed to drop frames due to moving too fast for the phone to handle.
My phone has also been running much cooler than it was before. The other problem I consistently had with it before was that it would get quite hot after extended use, which seemed to exacerbate the lag even more. I've been using the phone nonstop for over and hour now and it feels cooler than it ever did before.
The overall redesign is pretty nice too. I like the new font, notification and settings menus, and being able to customize the power saving mode is great too. It really lets you get the most out of the phone.