Okay, so...
Composition: There is a distinct difference between the two. They're both made by layering sheets sent in an epoxy, then pressed & heated until solid. The substrate sheets being either woven linen or bleached paper.
Visual: Linen micarta will have a distinct visual weave pattern, similar to linen phenolics of today. Paper micarta will have a "grain" similar to ivory, but no discernible weave.
Both are still made today. In my research, I've meet several custom micarta makers on Instagram that will make a custom batch for you. They mostly cater to knife makers. The problem is you have to order in a thickness suitable for ferrules. And the price is almost as expensive as finding the vintage material.
I've acquired several versions of vintage paper material, as well. GE made Textolite, another manufacturer made Marbalite, and so on. All are micarta; all are paper based. The "good stuff" most refer to, is actually Westinghouse Ivorite paper micarta. Westinghouse made other paper micarta - I have samples that are not Ivorite but still paper. Ivorite is what the majority of the vintage cue makers used. It appeared as ivory, was cheaper, not as brittle, and played well. However, as it aged, it turned the pale yellow you see on vintage shafts.
The reason for the price you pay, is once the vintage material is gone - it's gone. One has to search, and I mean dig, for a source thick enough for a ferrule. Some old cue makers still have some. Knife makers stock is usually too thin - even so, good luck getting them to let loose. It takes time, and then money to find it. All that is reflected in the price.
I'm a sucker for nostalgia, and sometimes get wrapped up in a subject. I've been researching this product for years. I've talked to Westinghouse employees, GE employees, Atlas Fiber employees (even the VP), cue makers, and knife makers in my search for information. And it's taken years to accumulate factual information, and would take way to long to type it out here. I hope this little bit helps.