Very well written by camieabz, very thorough and right about ram and also cpu.
You'll benefit more from an i7, the 7700k you're thinking of will be a good upgrade for your mobo and not spending more for another platform. There is truth in games nowadays utilising more cores/threads and Battlefield 1 is no exception.
Run Msi Afterburner and osd (on screen display) usage factors. There are youtube vids how to set up Afterburner if new to it. You'll see cpu usage in multi threaded games will be quite high on 4c/4t cpus. Games such as Ghost Recon, FC5, GTA5, Devision and FF, there are more and list continues to grow.
Ram nowadays, the old argument 8GB is enough is getting long in the tooth and seeing 16GB becoming the new standard is correlation to the amount of vram we have on GPUs. Pagefiles are getting to whopping sizes and SSD's speed is becoming more significant rather than just the old argument they're only good for loading and not fps, but how about the load stutters in game?. Games are loading more and more during game play due to massive open areas so having 16GB minimum, an SSD and a decent GPU and CPU will go along way.
My experience with Farcry 5 on a 2600k @ 4.5 with a 1080Ti is i've gained 20odd fps with Hyperthreading on. Only reason i found out HT can make a difference is i essentially had it turned off and checked cpu usage while playing FC5 and it was pegged at 95%, even though the game played fine, probably that 5% didn't cause stutters. Turned HT on and cpu usage dropped down to 60% and fps increased a lot.
Only bummer for me is Dying Light doesn't perform as well with Hyperthreading on so have to remember to turn it off before playing. But this is an oldish game not really designed for Hyperthreads whereas games nowadays are and continues to evolve.