i wouldnt breed an angora buck on a pygmy or nigerian doe. think of it like you wouldnt want to be average sized person (5.5ft lets say) having a baby with a giant person (9ft lets say). the size of the baby could be much bigger than a nigerian or pygmy baby and be nearly angora size but still has to get out the little bitty mom.
as far as the fiber goes... yes and no. F1 cross will have varying degree of fiber niceness and from there it gets better as you breed for it.
the fiber that you want is a wool hair, not the regular goat fur. regular fur is soft very short undercoat and the longer "guard hairs" which are thick and stiff and shed rain etc.
the angoras have been bred to make that undercoat really long and shiny. and they breed out the thick stiff guard hairs.
F1 crosses will have plenty of guard hairs in it still which spinners will not want and needs picked out. i have never tried it personally but seeing a few videos on it being done it is not something i will try in the foreseeable future, i just dont have that kind of patients
here is a site about them that has some good info
http://www.pygoragoats.org/
as far as meat or
milk from them... the fiber takes
alot of nutrients to grow. they could be butchered or milked. but expect probably half or less volume of milk from them and not to milk as long as straight pygmy or nigerian. angoras as well can be butchered or milked but they wont produce the same as a meat breed or
dairy breed.
a meat breed has been bred to make animals that turn nutrients into meat the best, dairy breeds bred for animals that make more animals that turn nutrients into milk the best, and fiber breeds the same to turn nutrients into fiber. so any crosses will work and you could milk a meat breed or whatnot but dont expect the same volume and quality etc from a true breed.
and with fiber animals you will have to deal with them being covered in fiber. i know angora goats are generally sheared twice a year and the fiber length is usually 4-6 inches. so if you were to milk an angora you have to work around that fiber.