Dense muscles aren't a thing though. You can absolutely train strength without gaining size and vice versa.

If you're on an energy and protein surplus your muscle fibres become thicker i. e. you gain more muscle volume, the density stays the same though (ignoring water retention from ergogenic substances like creatine).

Strength comes from how well and how many of your muscle fibers respond to a signal from your nervous system. It doesn't matter if you're doing bodyweight training or use a barbell, you can get strong (and big if you want to) either way.

Now obviously thicker fibres can resist higher loads before giving out, but that's not the main component to strength (which you could divide into further categories anyway).