To use a car phrase, "There's no replacement for displacement." (in reference to engine size)
It will help, but its not going to be any kind of miracle for speed, it seems most things now love sheer size and not always speed of the ram.
M.2 on the bottom? I dunno how I feel about that, its something you don't always need access to, but when you do you'd have to take the motherboard out. I've built several mITX boxes, none had access to the bottom easily.