Ideally, I would use two 140mm in front as intakes.
120mm will do. Yate loon 140mm fans cost about $8 each if you want more.
If all your intakes is in one place and filtered, your case will stay cleaner.
I am not a fan of aio coolers, but since you already have one, I would mount your H55 in the rear, exhausting out.
If you install any more fans, you will tend to draw in unfiltered air from adjacent openings.