@manuel-arguelles,
mainline kernel offers the best support of the available hardware, and all GPU works much better there, as far I/O, the mipi dsi and csi only work in legacy(but that is coming fast to mainline). but those shouldn’t really be much of a problem for your workflow.
as for the wifi/usb interference, the VIM3 received a hardware revision just a while back fixing various issues and titbits, I presume they solved that problem in that while, I even asked, but I didn’t get any official confirmation, but I haven’t really faced such a problem because of it,
as for accessories, its really what you’d like to have to improve your experience, monitor, mouse, keyboard, and a USB-C powersupply greater than 12w is best, you can go for the official khadas powerbrick sold in the store (24w) if you don’t have that around.
I also suggest purchasing the case,and the passive heatsink if you want to packaged solution. (if you work becomes intensive, the regular VIMs heatsink and 3705 fan, would be better than the passive heatsink)
I’d also suggest you to pick up 1 or 2 SD cards for extra storage, or better use an SSD for better, faster, more reliable storage. also since it switches the USB3.0 to PCIe, and hence you won’t get any problems from the wifi interference.
If you go for the SSD, pickup the size of SSD you want, but the type should be NVMe, other types won’t work, some of the working SSD’s are available in this list. and you also need the M2X expansion board to mount the SSD.
I hope this finds you useful. 
stay safe, good day!