Then check with your friend for the required performance level.
As guidance:
WX4100 = RX 560
WX5100 = RX 570
WX7100 = RX 580 (there Polaris cards are getting old and pricey for what they are, but are compatible from Sierra onwards and are all single slot, which may be handy for compact builds)
WX8200 = Vega 56
WX9100 = Vega 64 (the Vegas are the top dogs, but quite expensive; work from Mojave onwards)
W5500 = RX 5500
W5700 = RX 5700 (less powerful than RX 6600, but work with Catalina and Big Sur)