DRS
No equivalent. Proxmox has HA and manual migration, not continuous load balancing. Teams that leaned on DRS usually end up sizing hosts with more headroom instead.
What does not move cleanly
Proxmox is not a drop-in replacement for vSphere. These are the gaps that decide how hard a migration is. If you depend on several of them, the honest answer may be to stay where you are.
Site Recovery Manager
No equivalent orchestration. DR becomes replication plus a documented runbook, which you have to test yourself rather than press a button on.
Fault Tolerance
No equivalent. Workloads that genuinely need lockstep FT are the strongest single reason to stay on VMware.
NSX microsegmentation
No like-for-like. Proxmox has a firewall at cluster, host and guest level, and SDN, but policy has to be rebuilt rather than exported.
Distributed switches
Rebuilt as Linux bridges or OVS. Functionally fine, but the configuration is per-host and has to be managed rather than inherited.
vSAN
Ceph is the usual target, but it is not a like-for-like swap: different failure domains, different node-count and network expectations.
Backup
Check what your product supports on Proxmox before assuming the licence carries over.
Windows guests
Paravirtualised drivers and a guest agent per guest. Straightforward, but it is per-VM work that has to go in the schedule.
Written from what we see repeatedly. Your estate decides which of these actually apply to you — that is what the assessment establishes.