Yes, and yes.
Their Android app feels like an exact clone of the Google Photos Android app.
To access it remotely, you can use Tailscale like someone else mentioned. But you need to have Tailscale installed on everyone's phones.
You can also use a Cloudflare Tunnel to allow it to be accessed over the Internet without exposing anything from your home network directly to the Internet.
The latter is useful when I want to share a secret link to a photo album after hanging out with people so everybody can upload the photos they took to one place (something I used to do a lot with Google Photos)
Yep. Tailscale uses wireguard under the hood so that setup sounds exactly the same.
The Cloudflare tunnel is free. They don't seem to have a traffic cap either. They'll charge you if you want to use a non apex domain (e.g. subdomain) or if you need their more advanced bot detection/defense products. But a basic/standard setup like what us self hosters have is free.