If you get the correct type of regulator it will work with both side & top entry bottles, like the one I posted the link to.
Newbie question, how does that work with a side entry bottle ?
https://www.ebay.co.uk/itm/Argon-Re...993721?hash=item2ac98b91f9:g:8-wAAOSwJK9bfZQG
That type will screw into either type of cylinder then you rotate the flow meter so it sits upright.