A few months ago, I decided to rent the WFT-R10A wireless transmitter for a shoot to see how it worked compared to my usual tethering in the studio and compared to the built-in wireless in the R5. In a word, it sucked. Transfer speeds seemed no faster than with the built-in wireless. Shooting cRAW+mJPEG, it took 10 seconds easily per frame. Maybe OK for still-life, but that will never ever work for shooting on figure stuff. With my older XPS15 2-in-1 I crank along at about 125MB/s transfer with USB 3.1.
I read up on the transmitter. It supposedly uses 2x2 MiMo which I thought was supposed to speed transfers etc. I then thought, is it because my laptop uses 802.11ac, not the latest ax?? I'm pretty techie, but networking et al has never been my strongest suit. I know I can buy an Asus WiFi 6 stick for $70, but I don't want to waste the money if it really doesn't do anything.
On an editorial note, it seems camera manufacturers are always years behind with camera wifi. With large file sizes etc. I feel we are still working in 2010 in capabilities. Maybe shooting small JPEGs is all it's good for, but that doesn't cut it for most commercial photographers.