A sling is akin to a holster. The Vickers style of sling is what I use on all my rifles and shotguns, except my 14" Mossberg 590 where a two point sling interferes with the Streamlight forend, so a single point it is.
I wouldn't bother with a padded sling if as you stated, are transitioning (I assume shotgun to handgun), as the pad isn't necessary and can feel bulky and in the way when moving the shotgun and sling around, especially if wearing a tac vest or webbing. A padded sling is beneficial if carrying the shotgun slung for long periods of time.
Single points have their use, but I'm not a fan of them in the situation where you are working with your hands and your rifle or shotgun is dangling around your body like a Christmas tree ornament, however, if you are wearing a tac vest, webbing or kit belt, you can rig up a circumferential securing strap/lanyard to solve that.
If you go with a two point on a pump action, experiment with your mounting points to ensure you can work the action without interference and that you can maneuver it easily. Magpuls tube mag/barrel clamp is handy for a side mount QD or clip point option that can be positioned fore and aft.