Have you also considered the Norse Folkmuseum - an open air museum of historic buildings from the region? We spent all day - I am an open air museum enthusiast, I know not everyone is. (oops -edit, recommended above also)
https://norskfolkemuseum.no/en/the-open-air-museum
Fram Museum - I was surprised how much I enjoyed this. I'm sure we didn't spend more than 90 minutes, so possibly a quicker stop. Kind of "old fashioned" with signboards, but a lot of info in English that I enjoyed. Good if interested in polar exploration and history.
Kon-Tiki Museum - across from Fram. Another quicker stop. If you've seen the 1950s documentary or more recent movie re-make, this was an interesting stop.
Museum of Cultural History is farther out than the others from central Oslo. We didn't make it there as other spots were easier to access and combine.
Munch is very well curated.
As mentioned, the National Museum is quite good and convenient. Art and history under one roof!
(June 2023 trip)