Our drivers all use the 30mm kart and our biggest driver is about 180. Honestly if you’re just starting, it probably won’t matter if you go with the 30 or 32, you might not even feel the difference.
The Vortex TaG engine, the Rok TT, isn’t as popular anymore, largely because the Leopard was just as fast, if not faster, cheaper, and just as reliable. The Rok is a super nice engine, it just didn’t enjoy the popularity the Leopard has. And the Leopard is now being phased out in favor of IAME’s newer more reliable engine, the X30 which is a nicer package overall.
Vortex makes other great engines for other classes are enjoy a strong following, but currently their TaG popularity has dropped off.