I don't know anything about the new DUB cranksets and I believe its a whole different bottom bracket setup, but Ill leave that to others who know more about that then me. For your other questions:
You'll only need to know the BCD if you just want to just replace the crank arms only and use your current chainrings. BCD (bolt circle diameter) is the measurement of the circle through the center of the chainring bolts. For the 5 bolt shimano cranksets, 130 BCD is normally the size for standard cranksets 53/39 and bigger while 110 BCD for mid-compact cranksets 52/36 and smaller. Also in your case, I think it could be a it hard to find new 5 bolt crank arms as shimano has moved to a 4 bolt pattern.
If you're planning on going to a powermeter and buying a whole crankset you'll just have to match your current crank arm length, chainring size and bottom bracket as long as you just want to match your current set up and not change anything.
Im sure others will offer more information as well.
You'll only need to know the BCD if you just want to just replace the crank arms only and use your current chainrings. BCD (bolt circle diameter) is the measurement of the circle through the center of the chainring bolts. For the 5 bolt shimano cranksets, 130 BCD is normally the size for standard cranksets 53/39 and bigger while 110 BCD for mid-compact cranksets 52/36 and smaller. Also in your case, I think it could be a it hard to find new 5 bolt crank arms as shimano has moved to a 4 bolt pattern.
If you're planning on going to a powermeter and buying a whole crankset you'll just have to match your current crank arm length, chainring size and bottom bracket as long as you just want to match your current set up and not change anything.
Im sure others will offer more information as well.