@Adamonic
Thanks for the suggestion, I've cleared the cache and tried a few games.
The FPS has been slightly improved, about 45 FPS.
It's almost within the FPS average of my 128-player map, 45~55 FPS.
This is why I keep complaining about why there is no 64-man map to choose from.
My computer can't play normally under the 128-player map.
It seems that it will be another week of suffering, and I can only see if I can get a little luckier and finish the weekly tasks as soon as possible.
BTW My POOR PC :
CPU: i7-9700KF
menomy: 32G 3200MHz
SSD
GPU: RTX 2080