If for some reason Wifi performance cannot be improved (e.g. by relocating the router or adding Wifi repeaters): Instead of buying some pricey gaming laptop or mobile workstation, it may be much cheaper to get another Wifi router that will be set up right next to where you watch. It doesn't even have to be connected to the internet or your internal network if its sole purpose is being a wireless network switch delivering downloaded VR vids to your Q3.
a) Choose a router with NAS functionality and built-in DLNA server. Transfer video files from where you store them (laptop?) to an USB drive (preferably portable SSD with high write speed, not a cheap thumb drive) and plug that drive into the porn router via USB (USB 3.0 should suffice). On Q3, access the Wifi of the porn router and play via DLNA.
b) If the additional USB drive is too much hassle, it may also work to schlep the laptop to the location where you watch and connect it to the dedicated porn router that is also located there via ethernet cable. Enable file sharing in the OS of the laptop, and the laptop will act as NAS/server, while the router acts as wireless network switch. Q3 will then access the laptop's storage via SMB.
None of these options require any high(er)-end graphics card, they just make sure the data are transferred to the headset wirelessly from a close distance while the decoding will take place on Q3.
It may also be worth first looking into connecting your VR video storage directly to your primary router. If the data do not have to be transferred wirelessly from the storage to the router while in parallel data are transferred from the router to the headset, this may free up Wifi bandwidth.
It could also work to connect some old router that you may still have to your primary router (by ethernet cable or Wifi), set it up in the middle between primary router and headset, and let it act as a Wifi repeater (if your primary router supports that kind of thing).
