I really like elforyn and carbon fiber for spacers. when done right both can be very subtle and bring just a little modern touch to a handle. Elforyn is one of the easiest materials to work carbon fiber can be a bit of a pain.
I use the super thin g10 for liner and spacers. It's very subtle and you can barely even see it in photos. Paired with black dyed epoxy, it makes the joints look really clean. It's so thin there's really no effect on workability. Just need to be extra careful with fiber materials in general for your lungs, but you already know that.
There are all kinds of spacer material that is easy to work with & glues up nice. Metal can be a weak spot in wa handles if dropped & is harder to work.
Not knocking others taste whatever you like is fine. I like simple horn & nice wood, or a couple different wood glued together. More is not always better. Simplicity.
I use G10 a lot. Easy to cut and work with. Comes in various sizes, colors, and shapes. In the photos it is in sizes for liners, handles, and rods. I really enjoy making colorful knives, hard to find another material that is as colorful.
I have used vulcanized paper before and did not like it. Seemed too weak. I think it is basically paper with epoxy embedded into it, similar to Micarta I guess, but was not a nice material.