Wireguard

wireguard has a few setup scenarios. each are unique.

windows client

download, run installer, add empty tunnel

[Interface]
PrivateKey = (it should auto populate this for you)(public key is above in text field)                          
Address = (the ip you want on the vpn net/32 for one ip)

[Peer]
PublicKey = (find it on server)
AllowedIPs = (what you want to be able to connect to on vpn lan)(usually its the vpn router's ip, and then the lan range behind the router)
Endpoint = (ipaddress:port)

Optional: If you have a windows server w/dns (i.e. domain) don't use the vpn router but the windows server as the DNS. However, you may want to also add some other dns (level 4 / google) as backups. e.g.

[Interface]
PrivateKey =                        
Address = 
DNS = (windows server and the subnet should be on allowed ips, if it isn't already), 4.2.2.2, 8.8.8.8

troubleshoot that with nslookup. You might think you can avoid this and hardcode the dns in window's /etc/hosts but that won't properly resolve the domain controller. and everytime you access a domain share you have to enter a password. bad idea.