I regularly drive two 4k displays at 60hz with my 9300 and the TB16 dock. It will consume more power to run that many displays, but if the cooling system is functional, it should have no issue keeping up. 
I'm about to pull the trigger on an XPS 13 9310 with the OLED screen, i7 CPU and 32gb ram. I have one question left to answer that I can't seem to find online. Can this run dual 4k screens at 60hz through a dock like the W19TB(S) easily? I know it probably can do it but worried it might cause it to heat up or use a lot of CPU drawing the screens like my work laptop does. Does anyone do this currently and can they report on any noticeable impact to performance? Thanks for your help
XPS 13 9310 - Dual 4k through docks?