I can’t seem to find the exact place where it’s stated but I am sure I’ve read Emre saying that he expects people to buy a licence per restaurant even saying that we shouldn’t cheat. VPN would count as cheating in my book.
Our fiber connections are 500Mbit/s, ADSL 100Mbit/s and our 4G modems are 225Mbit/s theoretically but on average we get around 50Mbit/s. Bandwidth won’t be the bottleneck, processing power at the server is more of a concern for me. Also on the very rare occasion both fiber and adsl dropout the connection will fallback to 4G which has a very high latency, I will have to test and see if the latency is acceptable.
Here in NL we get very good and cheap internet but I think you are right when you say a 20MBit/s connection will suffice on a setup where you have max 10 terminals.