There are more than 100 museums in Paris, and all are worth visiting. If you feel like visiting more than 4 museums during your trip, we recommend purchasing Paris Museum Pass. It allows saving on admission fees, but more importantly allows skipping the line in most museums, including the Louvre Museum and Museum Orsay, two of the most popular (and crowded) museums in Paris.
It also makes sense to check if the museum you are interested in has an app and/or an audio-guide that can be downloaded online before your visit to the museum. This will help save several €s, and help navigate through the museum.
Audio guides, if not available online, are available at most museums, and these are often multilingual. An audio guide is a very helpful tool to learn about the collections and history of the museum.