1. Laptop output is more than enough.
2. More like this IEM is half the price of a well known brands bullet-style IEM. I have a feeling that the etys got tuned a lot more and will always have better details.
3. Yes, there is a chance.
4. Based on a quick search, almost every review says that MK5 has recessed treble. Yes, you are hearing more treble. Also salnotes reviews usually say too much treble.
5. You have not tried EQ-ing them yet?! Its almost step zero for me to apply an autoeq/oratory1990 EQ on any pair.

• EQ
• Use foam tips to lower treble (and eq down the excess bass maybe)
• Get some actually good tips to tune your IEM: https://www.audioreviews.org/guide-to-iem-silicone-eartips/
• Try tips you have lying around.
• Get something else. Planars almost always have great technicals compared to dynamics. Trn rosefinch and Celest pandamon are stupid cheap right now.

I have the Etymotic ER2SE and they are better than the Salnote Zero. Like you, I had been disappointed with the Zero, but only until I changed the silicone tips from the Red ones they came with for the Yellow ones. In my ears (we all have different lugholes) the yellows silicone made a better fit and got in deeper. This made the Zero a LOT better. Not Etymotic better, but still for £25, they are being kept.