What B88 said!
Playback: I'll let others contribute better than I can, but I go clean and uncoloured, a simple computer (I go stored music not streamed), DAC, speakers.
Software: If you're a musician I'd say Logic Pro or Ableton. If you're more of a recording engineer type, then ProTools is the best (sorry, but it is, can't do plugin latency compensation on any other), Reaper is also excellent and possibly the best for ambisonic mixing. If you are more creative then there's MaxMSP, Pure Data, Supercollider, Csound etc etc etc. For live coding, I'd try SonicPi. There are hundreds of other software tools, I just hit the main names, too much of it is fashion, no one cares what software was used to make a piece, if you're happy with it, then stay happy with it.
Instruments etc: I play piano and guitar badly these days because I don't practice. I still write scores by hand (pencil and paper) because I loathe scoring tools - I happily pay people to put my scores into Sibelius. But really any instrument can be used for composition, the most important tool is imagination.