In terms of speed, we'd say the sweet spot to aim for is around the 3000MHz mark for DDR4. For DDR5, We'd say to aim for 4800MHz and above, although at that point it really depends on your coffers ...
The best mini-ITX PC case is about being able to build a powerful gaming PC into the sort of footprint normally given to a games console. It's a challenge for sure, and the need for more expensive ...
The Seaberry is one such design, as demonstrated by [Jeff Geerling], giving the CM4 a Mini ITX formfactor and a ton of IO. (Video embedded after the break.) The Seaberry sports a full-sized x16 ...