I have crypts growing well in both environments, substrate only and substrate plus water column fertilizers. Both are growing very well. I use Flourish tabs to fertilize my substrates but I don't treat the crypts any differently than everything else, I distribute the tabs evenly throughout the substrate regardless of the position of the plants.
I have C. wendtiis happily growing in my tanks. All fert is water column. I have always been uncomfortable with root tabs since invariably, they will be stirred up somewhere along the way when you uproot.