Optimizational relevance in my configs bear these three:
fast-io
rcvbuf 524288
sndbuf 524288
Note that --fast-io has no effect on Windows.
The receive and send buffers are 512K and may improve performance that way. The Windows standard on Win8, for example, is 64K receive and 8K send, if I remember correctly, so adjusting these may really help.
Apart from that, I remove the 128/192 bit AES ciphers. What you could try is using CHACHA20-POLY1305 here, but I think it won't help your throughput at all on a PC. It could help on Android or routers, though.
data-ciphers AES-256-GCM
.