It depdends on the mainboard.
Some epyc mainboards have oculink ports onboard.
If you don't have them you could get retimer (pcie 4.0 and newer), redriver or passive pcie cards (pcie 3.0 and older) for connecting to u.2/u.3 backplanes.
Example for a pcie 4.0 redriver add on card:
AOC-SLG4-4E4T | Add-on Cards | Accessories | Products - Super Micro Computer, Inc.
What options for chassis should i look into, supermicro preferred?
if you want to go the 4x u.2 ssds route you could look at the 4u/towers 743 or 745 and replace the existing backplanes with a 8x sas/sata 4x u.2/4x sas/sata backplane (BPN-SAS3-743A-N4, I got two from ebay for ~120€ each)
Another 4x u.2 option is the 826 chassis, there are different options for backplanes (passive, single & dual expanders)
For 8x u.2 there is a 747 chassis with a 8x u.2 bay and the 846 with the expander backplane.
If you don't plan to use 3.5" devices you could get a 216 and replace the backplane with the 24x u.2/u.3 backplane (BPN-NVMe3-216N-S4, 400$ at wiredzone)