The initial reviews for the Dan / Lian Li A4-H20 have been released to overall very positive results. Like any SFF system, there is a build order that can make or break your experience. Unfortunately, some reviewers decided not to follow that order. Well, actually, maybe it's fortunate because their misadventures can show you exactly what happens if you don't read the manual. Ahem...Bitwit...I'm looking at you.
For those that don't know, the A4-H20 is the follow up to the original and now legendary Dan A4-SFX. The H20 version is actually a bit of a spin-off of the original C4-SFX design, repurposed into one of the most compact and space efficient designs that can still hold a 3-slot full size GPU, and a 240mm AIO. Using this combination, in conjunction with a powerful SFX power supply can yield a system that could basically be a match for the highest-end hardware available today. Well, almost. The 12900K is in a league of it's own to cool even with a 360mm AIO.
My ideal build for A4-H20 would be a Ryzen 5950X combined with an RTX 3080 three-slot variant. Whatever AIO I used, I would replace the fans with Noctua 120mm A12s exhausting out of the top in a negative pressure setup. The 5950X can easily be cooled by a 240mm AIO, and the GPU will see a substantial boost by having the negative pressure system.
Enough of my hypothesizing. Check out these reviews below.