Please set up Tailscale or a Wireguard VPN before you start forwarding ports on your router.
Your configuration as you have described it so far is setting yourself up for a world of hurt, in that you are going to be a target for hackers from literally the entire world.
Realistically, yes. But it’s a phrase and it’s important that they start doing that first. Maybe it’s their intention to do it publicly.
Also, sure, but a Wireguard installation is going to be much more secure than a Nextcloud that you aren’t sure if it’s configured correctly. And Tailscale doubly so.