1. Only thing I can add to Lloyd's post is that the materials do make a difference, but for what we build it's not noticeable. Metal film leads to a lower noise floor, especially at higher values. So for example, if you built a pedal with Carbon Comp, Carbon Film, and Metal film exclusively, the Metal film would have the least noise, the Carbon Film would be in the middle, and the Comp would be the 'noisiest.' So for that reason, Metal film is considered 'hifi' and carbon comp is considered 'mojo'. Carbon Film is common, cheap and easily a good middle ground. You cannot go wrong using any of those three types.
2. I wish Smallbear had more pictures for their products sometimes. I recommend:
Ceramic for values between 1 and 99pF
Panasonic film for values between 100pF and 920pF
Topmay or Panasonic Film for values between .001mF and .92mF
Topmay or Panasonic Film for Bipolar 1uF
25 or 35V Aluminum Electrolytic caps for polarized 1uf and higher.
Jacob