VPN for Windows

It's not easy to determine the best VPN for Windows, except those on Windows servers. The most stable one is PPTP but it's really out-dated.  

L2TP/IPsec such as npppd may not work properly on newest Windows. Embedded routers may still work.

OpenVPN may be a more universal across platforms. Noted that Mac, iOS, Android does not need the 'dev tun' line, while Windows or Linux/BSD required. Windows especially needs the 'dev tun' or 'dev tap' exactly the same with that on server! Otherwise WARNING occurs in log and ip cannot be fetched. Keep on waiting TUN/TAP interface...