>>7296029I think of them more as smaller more customizable GI Joes, I at least focus more on the figs and vehicles compared to lego where my focus is on buildings over the latter.
Brickarms seem to work with MC albiet they stress the hands slightly, a fault with making hands out of a harder plastic.
They are pretty compatible with lego bricks, as for cross compatibility with different lines of MC, I noticed there is an issue with arms being longer or shorter and not being a good fit for swapping, as well as some torso belt issues. Pic related.