As reported and demonstrated at Serious Cubase 9 VSTi Timing Problem (Bug Report!) - Steinberg Lounge - Steinberg Forums Cubase adds VSTi monitoring jitter equivalent to the audio interface’s reported input latency. Using essentially the same setup, Reaper does not do this (as shown below).
I guess trying to get Steinberg to fix a problem they’ve apparently known about (and likely how to fix) for over 9 years is futile (see “Live MIDI Buffering Jitter” at Solving MIDI Timing Problems). It’s unfortunate that they apparently prefer to obfuscate known problems (via both “Technical Support” and this forum) rather than properly address or even acknowledge them. 