It's the gluten that glues the bread together, so the stronger the flour, the more gluten it's got, the less fluffy the bread should, theoretically, be.

That makes a lot of sense! I may try a different flour, or maybe a mixture of all purpose and something else.

Yeast cooking is something I will leave until later...the idea of kneading, etc., is a bit daunting to tackle before I master simpler things.