"1. Intel Optane vs Femto SSD, both powered through motherboard - The Femto SSD sounds a lot better in the high frequency area but only slight better in the rest of the spectrum. It seems to take the hash out of the system. Some recordings would create listening fatigue with the Optane drive but less with the Femto SSD.
2. Femto SSD powered from motherboard vs Femto SSD powered using Paul Hynes SR4 - I think this is where it shines more. The external power creates more continuous or analog sound. It has more of everything - blacker background, cleaner highs, well defined bass, bigger soundstage. The soundstage depth seems to remain the same in both the case.
3. Intel Optane vs Femto SSD powered using Paul Hynes SR4 - the differences are even further apart than (1). The Femto SSD powered using a quality power supply is the key. It creates a very refined sound and once you hear it, its difficult to unhear it."