Under normal circumstances they can't.
They will just see your home ip.
The only indicator could be the added latency which is not really something you can change, but you can also tell them you are on bad wifi, tcp on the other hand maybe works a little better.
the difference between udp and tcp is that udp does not have a keep alive mechanism, so if a packet is lost it is lost contributing to more latency, tcp resents the packet this way you may lag less because the home server must receive the packet.
just to explain this further:
vpns encapisulate hops, so your public ip turns into the companies one, and the endpoint visible at the remote company is your home ip from the server.
It is not possible for them to do any of the deep packet inspection or look into your tunnel.