Tail up is hands-down more accurate in a smoothbore, contrary to intuition. Don't ask me why, it just is.
No idea how it will work in a rifled bore but I would think a wad of tow between ball and powder would be a big help since the paper alone won't be thick enough to seal the ball in the bore. Might be fine if you make a regular paper cartridge that is long enough to hold a full charge of powder and you crumple up the long tube under the ball and seat it that way. I'd make the cartridges dry and stick the whole tube in my mouth to get it wet after tearing the tail off and dumping in the powder. You can also glue a dry .45 revolver felt wad to the side of the tube, tear it off, and put it in the muzzle before the wad and ball to keep the powder dry when you ram the whole mess home.
However, it seems like a lot of trouble versus just using a pre cut, pre lubed cotton patch. If you want speed in loading, one option is to cone the muzzle and use pre measured tubes of powder that hold a ball in the other end and attach a small stack of pre-lubed patches to your bag strap or shirt with a safety pin......or make a loading block like has been done for centuries.