I really can't see any difference between my "typical" "giant" and "thinleaf" forms, and only a slight difference between "typical", and "wideleaf". The all red form is the only markedly different form (other than albino) that I have yet seen. The maximum size would be about 5-6 inches tall, and 4-5 inches wide at maturity with good culture for the "typical".
Remember these descriptions are all relative. I keep trying different named varieties in hopes that some will be really different, but I haven't seen this yet.
Nonetheless, capensis is a beautiful and impressive plant.
If anyone knows the origin of the all red form, I am very interested in hearing about it.
Capensis like most of the South Africans prefers cool roots, but this is a very adaptable plant, and probably would be ok with your Nepenthes. It does not *require* the high humidity, but it will be fine with it.