For motherboards look at these 2 that can take an EPYC Rome or Milan CPU
- TYAN Tyan Tomcat HX S8030
- Supermicro Supermicro H12SSL-i
With those cables you bought you could look at the LSI 9400 16i HBA which has 4 x SFF 8643 ports.
You probably want to RAID1 the Proxmox install not RAID0.