How big were the cultural difference between gallic or celtic tribes on the left/west of the Rhine and the germanic tribes on the right/east of the Rhine between the first century BC and the first century AC?

by bubim

From cursorily reading both Ceasar and Tacitus seem to make very clear distinctions not only between their own culture and the germanic people but also between the gauls and the germans.

How different were they really in their culture? Was there cultural exchange or spillover.

Also did the romanization of gaul have an effect on this?

Edit: Just to specify I mean tribes/peoples living in the border region not germanic and celtic tribes in general.