Those things, a block editor vs a page builder, are a bit different—but the idea going forward is that they will be able to work together in much better ways than in the past.
To make a change to layout for hundreds of page, I would suggest using a theme and in that case you would be able to change them all at once. Also, third-party developers may build ways to do that even with the Templates API from Gutenberg—we have yet to see.
I think you may be judging the page builder part too soon. Please consider testing the block editor and discussing here what you find about that.
