Benefits of quad channel support? Any AMD options?

Hi All!
I'm in the early stages of looking at a new PC build, and have noticed that X299 motherboards for intel CPUs support quad channel RAM
(as well as supporting up to 256Gbytes, in at least one case - which might eventually be handy (One use that I'm interested in is music
production with large sample libraries, which can get pretty big for orchestral scoring).

Not sure if I'd ever need to go over 128GB (at least for a long time), but I was wondering how much of a performance boost quad channel
memory (instead of the usual dual channel) would allow for things like 4K video processing and gaming - and are there any quad channel AMD options?