The latency of my presets (8 ms or below) is not enough for me to be bothered by it (I’m a sloppy player anyway 
) so this is all a bit academic for me.
It’s not a surprise to me, that using more than one physical core results in an increase in latency, but it is surprising that it’s 2.5ms rather than the 1.8ms “basic” round trip latency.
It’s even more surprising that using rows 1 + 3 and adding an effects loop to row 3 result in 9ms latency, and that’s before any blocks/processing is added!
I’m guessing that a preset using an effects loop in row 3 or 4 and a healthy number of blocks on top of that, will result in a total latency that is noticeable even by me!
But again this is all academic to me and I’m still very happy with my QC and the sounds I’m able to get with it.