For that power level I’d stick with a smaller 1 coil tank. These dual coil tanks work best at 50 to 70 watts and like a lot of airflow. 25 watts with these is far too weak to work well at all. My suggestion would be to look at the Wotofo Serpent SMM. You want a tank that can concentrate that low power vapor instead of diluting it. I wouldn’t go any bigger than that tank. An Augvape Merlin is a very good tank for 25 watts. I have one and it’s easy to coil and wick. As far as juice capacity, a low powered tank is going to generally be smaller and hold less juice, but it’ll made the best use of the low power to be enjoyable. Now if you could find an old Kanger SubTank. That works at a low power and holds 7.5ml! I have one of those, but they're so huge and awkward and would look ridiculous on my mod, plus I like something that can handle over 50 watts.