You will love bottom line. I use it on my machine on the top and bottom. Be careful, because some machines don't do well with it at the top, but I have never had trouble with it at the bottom.
No matter which thread you use you will still have to do some tension adjustments if you continue to see the tread show at the top. If the tension doesn't look so bad, it just shows a little on the top, the best solution is to use the same color on the top and bottom and always slow down your hands if doing free motion. Fast needle slow hands.