The Chick perspective:
I use both... like everyone else it is all conditional, for the most part I stagger my stance but still have my sholders and hips square to the target. Experiment with your feet how linear they should be. If your feet are too much one in front of the other you will lose balance and strength, too wide, and now you are straddle putting which might change your mechanics of release. After taking lessons from sprague he had me try widening my stance a bit.
I also straddle putt around objects, downhill (cause then i squat and it makes the grade of decline less), uneven footing or just cause thats what feels right when I walk up to my lie.
I practice both putting styles equally from all distances. I also practice putting around objects like trees or over bushes (hot tub
) I also jump putt quite a bit. I know that my shot will be up and down and wont miss to the sides. For a while, and even sometimes now I trust my jump putt more from great distances than I do my upshot. I have a great back yard for working on approach and putting. I go across the alley to the neighbors and work on approach shots anhyzer and hyzer around the bushes and trees.
Another way to practice putting is to get a routine, Make x amount of shots from where you are comfortable to start... that way you have the confidence when you move back... just keep going back till you are out of that comfort zone. Work there for a while, then go back into your comfort zone to regain confidence, control, and form, then march back out. Make sure to switch styles! And get the same mold of your putter so you can do at least three. I always use a mini and i always start my routine over for every putt. Remember everyone style is different, some loft or elevator putt, some go straight at it... find out what works for you!
If you hate putting, make it your new favorite!
p.s. i think its great that you cant go past 20 ft to start. Thats where they say you should make all your putts from. 30 is probably better... but you will have a solid range of where you know you can make your putts. Anything outside of your range that you make becomes a bonus. Eventually your range will be come bigger!