So people praise MTBs and track bikes both for having really nimble, good for cutting through traffic handling, but they seem and look like pretty different bikes/geometries.

Can someone explain this to a n00b? Which one has more nimble handling? Do like all those fixed-but-for-street frames hold on to the track nimbleness or push more towards a road bike?

Personally I’ve always gone the 90s MTB route but people are asking me for recommendations and I feel like I don’t know quite enough to give the best ones possible.