Oh right, so the NAS you can setup with the addon Samba NAS.

DuckDNS will mitigate your issues with not having a staic IP (alternatively theres any number of DynDNS programs you can look into if for example you already own your own domain name)

Nginx-Proxy-Manager allows you to forward ports based on the domain used to connect so, you might not even need it really but if you wanted for exmple to have an address like mysupercoolnas.duckdns,org rediect to one proxmox vm and mycoolassitant.duckdns.org to reditect to HA you could do that. Or you could just have one DynDNS setup and use port forwarding on your router to handle what ports direct to which VM.