Every Dapper Notes has the same 70lb smooth paper inside, and while it always worked well for my penciling needs, I often get asked about how they perform with fountain pens and other inks. I'm not exactly a fountain pen user, but thankfully Justin from Write eXperience offered to test, photograph, and review how Dapper Notes work with fountain pen nibs and inks.
Good paper thickness - not a lot of bleed through, appropriate for the 70lb weight.
No sheening properties.
Reasonable dry time - not great for lefties, but fountain pens can be problematic in general.
Some bleed at the edges - became more prevalent with thicker nibs and wetter inks. However, for a non-coated fountain pen friendly paper, this is actually good. Not as fountain pen proof as Tomoe River and Rhodia / Clairfontaine, but for a pocket notebook - pretty good!
Photos below show front and back of each sheet from Justin's tests, photographed by @writeexperience
If you have questions about Dapper Notes paper or anything to add, let me know.