Zero information how Rpi5 and the Radeon GPU are hooked up together, as if a port magically appeared out of nowhere to make this setup a total breeze.
I guess you could use the m.2 HAT to have a PCIe connection to an eGPU, but a PCIe 2.0 1x lane (500 MB/sec) is laughably inadequate for a video card - how do they get around that?
The Raspberry Pi 5, by itself, is great for emulating old-school games. However, Jeff Geerling has just shown that when paired with a decent discreet GPU like the AMD Radeon RX 6700 XT, the SBC can handle modern AAA games in 4K.