There are some low voltage track systems out there, but by and large it's 120.

You are right connecting pendants to track is usually an afterthought so most don't make a whole lot of track pendant fixtures, buy what you like and use the adapter.

There are three common track systems: Halo and Juno as you noted and there is also lightolier. Halo tends to be the cheaper and more common in my experience and you can get a second independent circuit (it's three conductor track) if you need it. Both the "house brands" at Lowes and HD are Halo compaitbnle track. You can't put a Juno or Lightolier fixture on a Halo Track (and vice versa).

Thanks this is helpful