The Tarataros bodies got eventually replaced by a new version so those should be fine. In terms of scale the heads they sell are the same size as classic Marines and Primaris, but bigger than Horus Heresy Legionary helmets. The backpacks are slightly bigger than the originals and the jump packs are the same size.  

I have some of their older Radical Gorobochick and I have been pretty impressed with their stuff.  But good to know about their CS and issues. 

I highly recommend the Tortuga Terminator bodies. I have their first pattern of Tartaros bodies and the most Cataphractii set. The old ones had some warping on the chestplates but that was easily fixed with a heat gun. If you do notice some quality issues their customer service is really good and they will send you a replacement if you show them photos of the parts in question.