Let me say that bugs and crashing aside, stutter, as well as hardware-related bugs, but purely fps and performance, your potato computer is your own problem. Your 8gb ram 3.2 ghz processor is the problem.
I have very consistent FPS on a rig I built in 2015. This is computer gaming, you need a gaming computer.
This game is nowhere near the level of mediocrity that M&B and Warband were in the visuals department. If you were expecting a game that you could play with the same toaster, then you were delusional from the beginning. It has been 10 years of advancement in gaming, and TW obviously was able to pour more resources into this title, yet somehow this game runs even smoother than Warband for me.
I love butter
Specs
16 gb DDR3 1866
i7-4790K 4 core 4.0 ghz
gtx 970