I don’t know of a good way to route other application’s traffic through the VPN container with them being in docker containers, unless you use some intermediary setup. That’s why I have socks proxies routed through the VPN, so I can selectively put traffic through it. If the app supports a socks proxy you could do it that way. At the least you could use Proxychains to do so if the program does TCP networking.

So it’s always going to be used for technical things, but not necessarily development things. I use it for both.

For my home server setup I have docker setup like this:

1. A VPN docker container
2. A transmission (bittorrent client) container, using the VPN’s network
3. An nginx (web server) container, which provides access to the transmission container
4. A 3proxy socks proxy container, using the VPN’s network
5. A tor client container
6. A 3proxy socks proxy container, using the tor container’s network

Usually it’s pretty hard to say “these specific programs and only these should run over my VPN”. Docker makes that easy. I can just attach containers to the same network as my VPN container, and their traffic will all go over the VPN. And then with my socks proxies I can selectively put my browser traffic over either the VPN or Tor, using extensions like FoxyProxy. I watch wrestling through my vpn because it’s cheaper overseas and has better streaming options, so I have those specific sites set to route through my VPN socks proxy. And I have all onion links set to go through my Tor proxy.