For me it always comes down to what is a good song and I'm very old fashioned in the way that I like to make songs that have something classic about them whether you can play them with an orchestra or an electro synthesizer or an acoustic guitar. ↗
If you're a guitarist, you should not be intimidated by using your instrument as a synthesizer, but you shouldn't feel that you have to own one, either. ↗
If it's fast, no I don't have enough piano technique. In that case, it's probably been done on some kind of synthesizer or sequencer. Then the score can then be printed out and so forth. ↗