Do Fuses make a difference ib sound?

It will be hard to test in a way that keeps you "blind" to the outcome. So, it will come down to your own ability to distance your perception from your preconceptions and desires. Good luck!

I take it that the fuses in question are 5x20 internal or 6x32. Not UK 6x25 plug fuse.

Fuses adapt over time to a device and work more OK when the difference between them and the board they are in is complimentary.

This means that a good deal of fuse are a waste of time. Also many fuse are not slow blow, so one should be considerate there.

To change and get an improvement I would recommend Aucharm (not slow blow) or Isoclean (either), I am fully impressed with Isoclean 10A and Aucharm other values. I ran tests on phonosophie and Synergistic Red over 10 years (just keeping an eye on them), and they failed my test of worth significantly.

I build power Cables for people in the UK, so we have them built into our Mains Plugs. Which is an absolute enemy.

Main power fuses inside the component can influence sound quality, and just like power cables - it depends. HiFI tuning fuses from Germany for around $100 is a safe bet (they are directional too). After running them for a week or two put the old fuse back in to gauge difference. I noticed positive change in Eversolo DMP A10 streamer/DAC, some improvement in PL integrated tube amp.      

If one has monoblock amplifiers, it would be easy to conduct an experiment. Just put an aftermarket fuse in one amp and leave the stock fuse in the other amp. You should hear a change in how the soundstage and imaging are presented from the side that has the aftermarket fuse. For me, it was subtle but audible. 

I would never put anything in a device other than a fuse of the recommended type. Aside from possible damage to the device, there’s also the risk of fire. I would really lose my s$!t if I burned the house down!