I would say the first part of Cumberland Gap is fairly accessible. You realize the tunes in his book were all ones that he recorded, him having already played for 20+ years, so not exactly entry level tunes and many beyond intermediate level. 
Here are some easier tunes to tackle if you’d like

youtube.com/playlist?list=PLsI...ZSFLmC0nw

I can't think of any thread that deals specifically with easy to hard to play Scruggs tunes.

Many of the tunes he played can be broken down to a beginner or intermediate level.

I remember my teacher started me out with Cripple Creek because it had rolls, slides, pull offs and hammer ons. At the time I thought it was terribly difficult, but it turned out to be fairly easy.

I guess you're just going to have to ask about a specific song and see if there is a beginnger or intermediate tab for it. I know Jack Hatfield sells Scruggs tabs for many of the tunes he used to play. Jack Baker has several free tabs for many Scruggs type tunes as does Chuckv97 and I'm sure there are others.

You might want to check the tab archive and look for whatever song you wish to learn and see if it specifies whether it's beginner, intermediate or advanced.

here's a list of tempos that might help
https://www.banjohangout.org/archive/278232

Many years ago there was a discussion here in which some experienced teachers and players expressed their opinions on a progressive re-ordering of the tunes in the 1960s Earl Scruggs book. "Progressive" as in how a student might approach the songs in a way that songs build successively on what came before. The reason for this is that the Scruggs Book is not arranged as a method or system. It presents the basics of notes, chords, and rolls. Then all the songs in no particular order.

FWIW, I find a lot of Scruggs tunes to be harder than I expect. I've been playing over 50 years, but my lessons did not necessarily teach  Earl's way of playing things. And I didn't own the Scruggs book early on so I never sought out his way. While I believe the basic rolls and roll patterns that I know are or include things that Earl did, my choices and preferences in the context of specific measures in specific songs are probably not the choices he would have made.

I experienced this when I tried to play Nashville Skyline Rag out of the 2022 Earl Scruggs Banjo Songbook. This is an easy tune for me: one I've been playing for about as long as I've been playing banjo. Earl's version as tabbed in that book kicks my butt. There are rolls or phrases that should be simple -- and I bet they are for all you folks who have "studied on Earl." But for me, who has played next to nothing  Earl's way, Earl's choices in this tune are so different from mine that they feel really strange and difficult.

I may try again. 

Mr Jack Hatfield should weigh in here. I am sure he would have a good take on this.
ken