The 4G connection allows for both, telemetry and video with low latency - providing you got a reasonable fast connection.
(Some mobile internet providers will limit data speed on pre-paid and low cost services)
Whist you certainly can use a different transmitter I would not recommend it for following reasons:
- More transmitters = more possible interference with other close signals like telemetry.
- More transmitters = higher likely-hood of problems with interference affecting FC
- Limited Range - from my own experience I know such transmitters usually only work well within 50m or so. But 4G could work even at the other end of the world providing you’ve got signal reception.
- Legal Problems - Many countries have legal restrictions in regards to transmitter power. Whilst there are stronger transmitter out you could get yourself into trouble if you get caught using such a device - Check with your local authorities.
Hope this is of some help.