One last post (some people pointed out the posts above and suggested I read them, nice reads, thank you all). If you stay off-topic, they'll fuss, so l'll bring it back around:
Another person has asked me to explain in detail why v18 "runs slower" than v17, etc. In v18, the author re-scaled the graphics settings. What used to be "the best" or High in v17 is now Medium. At Medium graphics, you should have roughly the same quality as v17 did. But an additional note: This game is severely unoptimized.
Note to Author: View [Lit->Optimization Viewmodes] as a start to view unoptimized areas (pretty much everything...). If you upgrade to Unreal Engine 4.23, you can use the new Unreal Insights tool to help you track things down. Check the Release Notes. If you spend a week optimizing everything, I'm pretty sure more people would appreciate that. It'd be less waste on the environment as well. Might encourage more Patrons, if that is your goal... You should also usually not disable In-game Console (I re-enabled it myself the builds I used to test why performance was low for others) as it allows people to tweak graphics settings such as changing the Ambient Occlusion, Shadow Quality, SSAO, etc... If you want, I can translate to Japanese, just contact sometime.