I am no clairvoyance but you don't need a high-end system for an actual PS4 emulation to work. The PS5 isn't supposed to have much higher requirements for the cpu or graphics card, but it should allow for quicker loading times by using nvme/ssd drives.
So, you probably don't need any better than the Ryzen 3700x anytime soon, and a rx 5600xt/rtx 2060(S) is more than sufficient for any actual gamesystem and very likely for the upcoming systems as well. 16gb of memory is enough, but you should go with a 2tb+ harddisk for the system(s) and any older emulation environment, plus a large nvme (qlc does suffice) for the upcoming generation.
You want it compact, so maybe go with a micro-atx mainboard and a compact case, like for example the Thermaltake Armor A30 which also allows to add a blue-ray and some hotswap-storage to it.