Have you verified that your ram is actually set to 3200? You sure it didn't default to 2400?
Are you running Geforce Experience, if so make sure it didn't "optimize" anything. Like, set a resolution scale or sth?
Verify power plan settings in windows?
Also, you could consider restoring W10 as one possible "workaround". I know it's a pain.
Ps.
AFAIK if you're running render scaling at 50% you're rendering the game at 50% of actual resolution, so you end up with a blurry mess. Suggest setting it to 100% unless you're really craving super high fps.
Alternatively this might be a result of some shoddy drivers or Ubisoft messed something up with latest update for the game.
Edit.
Hi, i built my new pc around 2 weeks ago and it was great, only downside is that for a couple of days my siege frames have dropped drastically. My specs: https://gyazo.com/f55b46200444c7295dfd69537cd38f1b Benchmark: https://gyazo.com/49e2517280ba32b1bdfe5f1e6d7d7c87 I play with texture on medium...
steamcommunity.com
Guy had similar FPS drop, reinstalled windows, FPS back to normal.