Sorry. You're right; he does have suggested itineraries for independent travelers. I've looked at those and had the reaction that they do not allow enough time at any major destination to cover more than a few of the highlights, however they might be defined.
The one-night stops may well be fine; there are certainly places where that's enough time to see most of what's there.
If you want to post the itinerary you're looking at, the more knowledgeable folks here can perhaps suggests which places are OK-ish with the time Rick allots and which need more time. Is it this one, from the website? (I think there may be something more detailed in his Scandinavia guidebook.)
4 days: Copenhagen, Stockholm (connected by a 5.5-hour express train)
[Here you have a total of less than 3-1/2 days for two major capital cities.]
6 days, add: Oslo
[Less than 2 days for Oslo, too.]
8 days, add: Norway in a Nutshell fjord trip, Bergen
[The Nutshell is a long day. How early are you going to get started the next day in Bergen?]
10 days, add: Overnight cruise from Stockholm to Helsinki
[That "overnight cruise" is a 17-hour ferry trip, giving you at best 1-1/2 days in Helsinki.]
14 days, add: Ærø, Odense, Roskilde, Frederiksborg (all in Denmark)
17 days, add: Aarhus (Denmark), Kalmar (Sweden)
21 days, add: Tallinn (Estonia) and more time in capitals
24 days, add: More Norwegian countryside or Stockholm's archipelago
I would point out that Oslo in particular has done a great deal of work on its waterfront. There's a fancy new Munch museum ("MUNCH"), and the consolidated/new National Museum is said to be the largest art museum in Scandinavia; it also has decorative arts.
These are the places Rick makes a point of recommending in Oslo (triangles are his ratings; I've edited his comments to save space):
▲▲▲ City Hall--Oslo's artsy 20th-century government building, lined with huge, vibrant, municipal-themed murals.
▲▲▲ National Gallery--Norway's cultural and natural essence, captured on canvas. [Now part of new National Museum.}
▲▲▲ Frogner Park--Sprawling park with works by Norway's greatest sculptor, Gustav Vigeland,.
▲▲▲ Fram Museum (Arctic exploration ships)
▲▲ Norwegian Folk Museum--Norway condensed into 150 historic buildings in a large open-air museum.
▲▲ Norwegian Resistance Museum.
▲▲ Viking Ship Museum Impressive trio of ninth-century Viking ships. [Currently closed]
▲▲ Kon-Tiki Museum .
▲ Oslo Opera House.
▲ Akershus Fortress Complex
▲ Norwegian Maritime Museum
▲ Ekeberg Sculpture Park--Hilly, hikeable 63-acre forest park with striking contemporary art and city views
▲ Edvard Munch Museum [New museum now open, probably larger]
▲ Grünerløkka--Oslo's trendy former working-class district.
▲ Aker Brygge and Tjuvholmen--Oslo's harborfront promenade, and nearby trendy neighborhood with Astrup Fearnley Museum, upscale galleries, shops, and cafés.
▲ Holmenkollen Ski Jump and Ski Museum
Norwegian Holocaust Center--High-tech look at the rise of anti-Semitism, the Holocaust in Norway, and racism today.
Nobel Peace Center Exhibit
How many of Rick's recommendations are you not interested in? Could you cover your Oslo hit list in 1-1/2 days and also have time to move from sight to sight and have lunch? Are there places not on Rick's list that might align with your personal interests? There are for me, so I have to allow extra time If I don't want to feel disappointed about missing key things.
For me all the capitals--plus quite a few of the smaller cities, like Bergen--have more sights to interest me than I could fit into twice the time Rick allows, and I like time to walk around the cities, too. If you spend all your time at museums and historic sites, how do you even know you're in a foreign city?