Hi Sergeiu.
I haven't found the realease notes for vQFX10K versions 17.4R1 or 18.1R1. That was one of my questions to Juniper SE as well (1. PFE image being RE image, 2. interface em4 on RE (light mode) not working and 3. release notes/documentation missing) . I will share once I will know more.
I do expect the supported feature set is aligned with physical QFX10K for these Junos version (throughput is limited on vQFX though). There can be certain limitations indeed (e.g. I noticed emX interfaces are not supported under routing-instances).
Hope this helps a bit.