Don't know the details of the Symetre rear drag, but a few points to consider:
* the rear drag MAY (you need to check this) allow you to change the spool without having to reset the drag;
* this is countered by the rarity with which you change spools and the general advice to back off drags when storing reels, to reduce wear;
* a small drag will initially work well but will heat up more easily and wear more easily. Threadlines have proportionally smaller drags than other reels so you don't want to go smaller than you need to. You need to check how the front and rear options compare