My fastest growing Plinias are the more common, standard varieties: Sabara, Grimal, and Escarlate. I have Reds, but for whatever reason, they have always lagged behind those other ones. Phitranthas also generally grow quickly, but I've found there is a bit more variation from plant to plant and variety to variety within that species. Nana is the slowest Plinia I have; it is a dwarf variety, though. Oblongatas vary wildly; I have one that grows well and two that don't. Blues and Yellows are similar to Oblongata with variation from seedling to seedling but a healthy plant will grow at a solid, if unspectacular rate. Rivularis is not a fast growing variety; water quality can set it back considerably. Never water it with anything other than rainwater if possible.
Now, I am only talking about vegetative growth, not time from seed to fruiting. My Sabaras and Grimals may grow vigorously, but they are not precocious varieties in terms of fruiting. Reds, Escarlates, and various Phitranthas are pretty much universally agreed to be the fastest fruiters, with the exception of Adam Shafran's Anomaly.