Oh forgot to say if you want HDR to display on an HDR compatible TV, the splitter has to be HDMI 2.0a (bandwidth 600Mhz/18Gbps).
The only one I have found that can do HDMI 2.0a at the moment is by LIGAWO & from reviews it seems a bit hit & miss :-(.
I know you said your Vellbox was 600Mhz, are you deffinately getting HDR on your TV when using PS4 (obviously not VR) if so I will go for the Vellbox (if answers "yes" can you put a link to the actual one you purchased please).