And what size would you recommend if I'm 1.68m tall with a 78cm inside leg and ride a Canyon Aeroad in size XS, which fits perfectly.
I am 169cm and leaning towards the 50cm frame for the LCR018.
What I did was take the current stack of my bike + the spacers. Then took the reach + length of the stem + bar reach to get a rough idea of what I currently. Current reach of 536mm and stack of 553mm. Compared to the LCR018 with what I wanted for my next bike, slightly longer and higher. That means the 50 frame, 100mm stem, 20mm spacer and the HBR17 bars will get me there. May not be perfect, but I think it is a good way to get an idea of what size you will want. Keep in mind the HBR17 have an 8mm rise, so I think that would act like an 8mm spacer (someone correct me, if i am wrong).
That being said, I have a pre-purchase bike fit coming up next month to help me confirm everything before I order. To be on the safe side.