OK, first thing to try with the ASUS ASIO driver is to set the bit-depth in the ASIO Control Panel down to 24 bit (instead of the current 32 bit).
If this isn't enough to get better results, try raising the latency value (from the current 4ms) next - while keeping the bit-depth at 24.
The same applies for using the ASIO4ALL driver. The current buffer size of 128 samples might perhaps be too low for your system to handle.
So try raising the sample value stepwise (to 192, 256, 512, ...) to see if this makes any difference.
Side note:
It's interesting that the ASUS ASIO Control Panel in your screenshot has a 32 bit-depth option, but the ASIO4ALL Control Panel shows 24-bit (as maximum) for the ASUS Xonar.
And the specs and manual for the ASUS Xonar Essence STX also seem to only list 16 and 24 bit-depth: (
ASIO Driver Support: 48K/176.4K/192K/44.1K/88.2K/96KHz @ 24bit/16bit)).
EDIT:
Just in case, also make sure that the same sample rate & bit-depth settings are used for all input/output devices in both Reaper and in the Windows Sound Settings:
https://answers.microsoft.com/en-us/...a-22efda8da0c2
As example: try using either
24 bit, 44100 Hz or
24 bit, 48000 Hz consistently to see if it makes any difference.