i would first install msi afterburner-
i hope the latest version will already work for windows 10 latest update,
you need a second program which does the overlay- this second program comes with the installation. - some tuner
the tuner hat compatible issues with windows 10 update some while ago.
after that you can monitor your fps, combined with cpu core/thread usage and gpu usage.
you will soon observe your bottleneck.
if there is no special mystic gpu driver problem related to dx9
i have the idea that one thread/core of your cpu bottlenecks it, not because your cpu isn powerful, but its simply influenced by the core/thread where all the network -netcoderelated management runs from the game- maybe your ping/latency is low and this influences the fps performance.-
whta is your internet - how much download/upload - wlan/lan? which ping to b&s=?