It is pretty much a universal rule that, the thicker the juice, the more problem you will have with wicking and the higher the VG, the thicker the juice. For the reasons yzer pointed out, even "100%" VG juice is rarely over 95% and is often diluted even more using water or alcohol in order to make it thinner / wick better.
More free-flowing cartomizers like the 801 Fusions (ikenvape carries these) will often work better for thick juices. Also, more and/or larger holes in the carto when used with a tank will improve thick-juice performance.
Clearomizers like the Stardust and ViVi Nova have, in my experience, real problems with thick juices; requiring constant tipping and not dealing well with chain vaping. However, a little bit of distilled water or pure grain alcohol can go a long way to thin out a juice.