I have panty line problems, too...the panties that work best for me are easy to find...the sell them at Taret...here's the link.
Target:Gilligan & O’Malley® Womens Ultimate 3 Pa...
There are plenty of reviews to read online, too. At my Target they sell them individually. Oh be careful, because these also come as a thong, so if you don't want a thong, check carefully, because a thong occasionally slips in with the bikinis.
I just stumbled on these as I was going from store to store trying to find undies that didn't leave vpls...I bought many pair that were more expensive, but these work the best for me, and they're comfortable and fit and look great.
And thanks for asking this question, because by looking for a link, I learned that Target sells these online cheaper than in the store and they can be hard to find in the store, too, so now I can just order some up the next time Target has a shipping deal.
I know how frustrating it is, so I hope these work for you!
Trixoo