PHS-memory is not a brand most builders will already know, and the CUDIMM format on this listing is the detail worth understanding before the name: CUDIMM is a clocked variant of unbuffered DDR5, built around an on-module clock driver that plain UDIMM doesn't have, and it only works in boards whose specification explicitly supports it.
Both capacities in this family run at the same rated 6400 MT/s CL52 — the choice here is between 32GB as 2×16GB rather than a trade-off in timing, since neither the clock nor the latency shifts as capacity goes up.
This is unbuffered, non-ECC DDR5 for a consumer desktop board, and the clock-driver requirement is the fitment check that actually matters: confirm CUDIMM support on the board itself, not just the socket.