Side stories in a novel.

I have begun to take a closer look at an idea I encountered in "the Wandering inn" Series by Pirataba. The main story is on the theme of the fool triumphant, save the cat story type. But in addition to POV shifts between characters, the author also inserts side stories into the series, which have different characters are are shorts embedded within the novel. These shorts are related to the fantasy world of the story, but instead of distracting from the story, serve to flesh out the story world from different angles. And in some cases bring up some very obscure trivia from our world. The author weaves in an abridged story about Emperor Norton the first of America, and amusing tale in itself.

While this Author makes effective use of this in the series, it strikes me as one of those techniques that will either work very well or fail dramatically. Where is the line for making this an effective addition to our writing tools, and leaving a project as a burning pile of ash? The way this author uses it, is the self contained story is about two chapters long. On a different continent from the main story, though some very general details of the area are mentioned in the main story, as the MC learns about the world they are in. The characterization in the side story is powerful, creating instantly likable characters.

About "the Wandering inn" Series by Pirataba.
While classed in the genre of LitRpg, it does not drone on about character stats, and the like, which has in many cases struck me as a way for the author to pad the word count of the work. Levels and skills get mentioned, but primarily in a conversational manner, and not the info dump of a detailed character sheet. As mentioned above it also falls into the Save the cat genre:
The Fool Triumphant
The ultimate Village Idiot, in which our fool must stand up against an establishment, ultimately exposing the establishment as the real “fool.” FT contains a fool whose ignorance is his or her strength and whose gentle nature makes him or her likely to be ignored (except by a jealous “Insider”), an “establishment” – a group or an institution the fool comes up against, and a “transmutation” in which the fool becomes someone new (sometimes communicated as a disguise or name change or new identity). FT also contains sub-genres: Sex Fool, Undercover Fool, Political Fool, and Fish Out of Water. FT examples: Being There, Amadeus, Tootsie, Mrs. Doubtfire, Legally Blonde, The 40 Year Old Virgin, Shine, Life Is Beautiful, Boogie Nights, Elf, The Artist

The above is from the Save the Cat description of genres.
From the writers POV, I view this genre as one of the more creative forms of the writing art. Where we must develop a problem for the MC. Then we have to ask what is the stupidest thing the MC could do here. Then get really creative on how we dig the MC out of their mess.