One can further tunnel SSH inside of TLS with Stunnel [0] to get through firewalls that block SSH but permit arbitrary TLS connections. Loading a website through this requires three layers of TCP but assuming the connection is good this should be okay.
A couple reasons for a regular VPN: they can be made automatic and persistent so the tunnel is always ready for use, they can tunnel other protocols besides TCP, they can tunnel entire networks, and using UDP as the tunnel protocol helps avoid the TCP-in-TCP congestion issues.
Yes, and piecewise TCP is often even faster than point-to-point TCP, especially on flaky connections, or when the transient connections are on hosts with lower RTTs (outgoing gateway closer to destination). It will likely be faster than a UDP VPN.
It still does have overhead, so lower bandwidth. Also, TCP, SSH and/or TLS forwarding of UDP, IP or Ethernet can have issues with delays, re-transmits etc (TCP-in-TCP).
It just relays the packet payload (i.e the actual data bytes inside the TCP stream are read out from the source, then sent along to the destination inside a different TCP stream. TCP/IP headers aren't included or replayed).
A couple reasons for a regular VPN: they can be made automatic and persistent so the tunnel is always ready for use, they can tunnel other protocols besides TCP, they can tunnel entire networks, and using UDP as the tunnel protocol helps avoid the TCP-in-TCP congestion issues.
[0] https://en.wikipedia.org/wiki/Stunnel