Hi Metro, look here, where I tested this manually. And of course I expect the volumio team to have done that, too. There is no noticable difference in device noise, but if I remember correctly, with speed 1x you have to be really patient when skipping tracks. So, yes, I would consider 4x to be the best compromise, too. It only should work.
Also If I remember correctly, the drive spins now more slowly, but not as slow as with manual setting. 
. So something is still wrong.
But back to gapless playback. I´m just assuming here, since I am not deep into system diagnostics at all. I have an external WLAN antenna (USB) on all of my raspis, which start blinking some 10 or 20 secs, before one track ends, which I think is a hint, that the next track is fetched and buffered (At least playing via spotify connect this is quite obvious). When playing CD the drive starts spinning up AFTER the track ends. Why? Solve this one and this could be half the way to get a gapless experience!
Cheers
Arnd