ROMED8-2T is one of the all-star boards of the modern era imo. Like that's literally "ATX-maxxed" in the Panamax sense - you can't go bigger than that in a traditional ATX layout, and there is no point to having a bigger CPU (even if you do not use all the pins) because it starts to eat up the space for the Other Stuff. It's a local optimum in board design and everything else past here gets weirder and has to start making more and more tradeoffs.

EEB/EE-ATX can push things a little farther (like GENOAD8X-2T) but you can't pull any more PCIe slots off, so it has to be MCIO/oculink instead. And imo this is the reasonable limit of what can be done with single-socket Epyc even in EEB, this is "EEB-max".

And you can't really get more than 8 memory slots without moving the CPU over to the other side of the board, like MZ32-AR0 or MZ33-AR0, which means it overhangs the PCIe slots etc. IIRC you can sorta do 16-dimm SP3 if you don't do OCP 2.0 (gigabyte or asus might have some of these iirc) and you drop to like 5 pcie slots or something. But it's really hard to get 2DPC on epyc at all, the layouts get very janky very quickly.

You can fit more RAM slots into EEB/EE-ATX with a smaller socket (dual 2011-3 with 3DPC goes up to 24 slots in EE-ATX) but 2DPC is as big as you can go with epyc in a commodity form-factor. In SP5 this gets fully silly, MZ33-AR0 is an example of 2DPC 12-channel SP5, and it's like, oops all memory slots, even with EEB and completely overlapping every single pcie slot.

And of course dual-socket epyc gets very cramped even on EEB/EE-ATX even with only 8 slots per socket (MZ72-HB0). You just are throwing away a tremendous amount of board space and you lose pcie, MCIO, everything. SP3 is already a honkin big socket let alone SP5, let alone two SP3, let alone two SP5, etc... they are big enough that you have to make Tough Choices about what parts of the platform you are going to exploit, or accept a non-"standard" form factor (it's not standard for anyone except home users/beige boxes). Servers don't use EEB/EE-ATX form factors anymore, because it just isn't the right shape for these platforms. And you need to be pulling a significant amount of the IO off in high-density formfactors (MCIO, Oculink, SlimSAS, ...) already, and your case ecosystem needs to support that riser-based paradigm, etc. ATX is dying and enthusiasts are not even close to being ready for the ground to shift underneath them like this.

(me when I see a honkin' pair: https://www.gigabyte.com/us/Enterprise/Server-Motherboard/MZ...)

There's still good AM4, AM5, and LGA1700 server boards (with ECC) btw - check out AM5D5ID-2T, X570D4I-2T, X470D4U, W680 ACE IPMI, W680D4U-2L2T/G5, X11SAE-M, X11SAE-F, IMB-X1231, IMB-X1314, X300TM-ITX, etc. And Asrock Rack and Supermicro do make threadripper boards too (WRX80D8 family, TRX40D8 family, etc), although I think they're not viable since threadripper is leaning farther and farther into the OEM market and it just doesn't make cost sense unless you really need the clocks. It's not like the X99 days where HEDT was just "better platform for enthusiasts", there is a big penalty to choosing HEDT right now if you don't need it, and it's generally too segmented to make sense.

Unregistered DDR4 tops out at 32GB per stick (UDIMM or SODIMM), registered can go larger. DDR5 unregistered will go larger, and actually a few 48GB sticks do exist already, but generally you can't use all four slots without a massive hit to clocks (current LGA1700/AM5 drop to 3600 MT/s) so consumers/prosumers have to consider that one carefully.

(this generally means that drop-in upgrades are not viable for DDR5 memory btw - 4-stick configs suck, you should plan on just buying 2 new sticks when you need more. And the slots on the mobo are worse than useless, since the empty slots worsen the signal integrity compared to 2-slot configurations without the extra parasitics...)