Depends on what mode you’re playing.
Primarily, there’s casual matchmaking, which actually is full of new players. Sadly, especially in off-hours, there’s also a lot of bots hosted by some mentally unstable script kiddies (no joke, they buy in a bot hosting framework and just pop that on a VPS somewhere) dedicated to ruining the game for everyone with aimbots, mic and chat spam etc. They abuse the fact that Valve hasn’t updated the anticheat in what feels like years. Regardless, there are still tons of healthy games to be found and bots usually are kicked within seconds.
Additionally, there are community servers which, depending on the actual community playing there, can have bonkers veterans or absolute noobs. These servers often are modded, too.
Yes to the routing, no to the port thing. A URL (i.e. qbittorrent.yourdomain.tld) is simply much easier to remember and work with than an IP:Port combination (i.e. 87.253.143.32:8080).
It also has a security benefit, because if you expose your server to the internet, you only have to open the http(s) ports of your webserver in your firewall and not the ports of the applications behind it. The webserver will do all the communication with your backend and then serve the information to the requester, so you have a buffer in-between.
Less open ports = less potential points of attack.
At least that’s how I understand it. I’m just a hobbyist, so if I got it wrong, feel free to correct me.
Frankly, if you want to use nginx as your reverse proxy and don’t want to get too deep into nginx configuration files and stuff, check out Nginx Proxy Manager. It’s a GUI frontend that automatically gets you SSL certificates for your subdomains, super useful.