N50 4x2 is ridiculously strong for any 3x3, provided they are the real deal (since many sellers on eBay will actually end up being N35, anyway). N35 4x2 will be far too weak for the GTS2 due to how thick the plastic is in that cube. In general, you want strong magnets for fast cubes and weaker magnets for slower and controllable cubes. The GTS2 is on the faster side, so I believe the best magnets for that cube would be N42 5x1, but you'd have to buy that at special magnet shops online such as Gaussboys if you're based in the US. The feeling of that magnet is strong, but not overbearing, and due to it being wider than 4mm discs, they feel a lot smoother and less bumpy or snappy.