d16 vs d8:
1. ram
d16 has more dimm slots, but unless you buy the much, much more expensive LRDIMMS, you won't be able to use them without losing performance. RDIMMS allow only 1 dimm per channel (4 dimms per socket) before DDR4 clock rate is lowered.
So, unless you already have or have easy access to LRDIMMS, you likely won't be able to make use of the extra dimm slots. You are better off getting 8x16G sticks for a total of 128G or 8x8G sticks for a total of 64G of memory.
2. PCIE slots - d8 has more, so if you ever want to do 4xGPU, the d8 will be better as the d16 can only do 3-way SLI owing to fewer physical PCIe slots.
3. ipmi - do you intend on using it?
Z10 vs EP2C:
1. PCIe - compare to d8 - can do 4x GPUs where d16 can only do 3.
2. performance:
a. clocks - all-core
- The Z10PE-D16-WS is producing all-core turbo for me at 50% 3.3 and 50% 3.4GHz (36 threads show 3.3 36 show 3.4 under all-core load).
- The EP2C612WS is showing 3.2 for 72 threads under all-core load
b. clocks - heavy real load (not synthetic)
- both show ~3.8GHz for 18-20 core jobs - real work bounces all over the place - indistinguishable by eye-ball
c. here's some geek-bench runs for you to judge - easiest thing for me to run right now (no windows)
Z10PE-D16-WS
https://browser.geekbench.com/v4/cpu/3047882
single: 4274 multi: 74436
EP2C612WS
https://browser.geekbench.com/v4/cpu/3047980
single: 4335 multi: 73304
single 2690v4 (3.5GHz chip) for further reference:
https://browser.geekbench.com/v4/cpu/3047837
single: 3803 multi: 39893
4.4GHz 6950x for even more silly fun:
https://browser.geekbench.com/v4/cpu/3048053
single: 4527 multi: 37496
Frankly, I'd call those (z10 vs ep2c) dead even (well within noise...). That sort of difference could be anything in either one of these two systems such as background processes (network, nfs, etc...)
If I had to wager, I'd bet the Z10 would put up tiny little fractions more in something like cinebench on THESE TWO SPECIFIC systems, but I don't see anything here that conclusively says you'd see the same other than the slightly higher all-core turbo.
Lastly, the EP2C612 was slightly easier to mod - run UBU, flash bios vs Z10 which is hand-edit bios, run ubu, flash bios.
You'll do fine with any of them, the EP2C is cheaper, so there's that...
EDIT: the EP2C 2.13b bios gave me a performance bump, but I'm not sure at this point whether it was the bios or something else I did... The 2.13b bios is NOT available on their website yet... So. factor that into "easy to mod".