Its personal. I press as little as possible.

I press each time. I think you get a more accurate reading that way.

if you press seams open you don't have a "ditch" to stitch in.

I press all of my seams at each step, for me, it increases my accuracy.
I press to the side and open too if the intersections are going to get too bulky :D:D:D

I press with each step. Partly because I think it would be tough to press them all just so after the blocks are all sewn together.

Always press - to 'set' the seam and then press to the dark fabric. Pressed seams are much neater. SITD is thru batting and backing so whether you are through the seam allowance or not doesn't matter.