Paris transportation apps and our bizarre experience

My family, which has experience using public transport during our travels, has had an interesting experience travelling from Charles de Gaulle airport to Paris and around Paris. FYI, we did not do the research on the best mobile transportation app to download before arriving. We ended up downloading the Bonjour RATP app, as it was the first one to appear on our phones. After taking the RER from the airport, we arrived at the Metro station needing to purchase a ticket. The only available ticket option on our app was for a bus/tram. No metro ticket option - very strange. We talked to a very nice woman at the Tourist Info booth, but she was surprised and wasn't able to help us. Yes, we could have waited in the long line and purchased a ticket at the kiosk, but we like puzzles and wanted to figure out this problem. Perplexed we purchased the bus tram ticket on our app as it was the only one listed. It turned out we were able to access the metro using this ticket - interesting. Now that we are in Paris, suddenly the Metro ticket option has shown up in our app. Next, my wife needed to buy an RER ticket to the airport for her trip to Vienna, but the only available option on the app is a RoissyBus ticket for 13E. Same price as the RER but is it the same ticket??? After some reading on this forum, a user reported that the Ile de France mobilites app was much easier and more logical to use. Both my wife and I downloaded the app. After the download, we see the one way Paris to airport 13E ticket on the IDF app. We went back to the Bonjour RATP app and magically, the 13E one way airport ticket also appeared on this app. Note, there is an option in the Bonjour RATP app that states "Can't see the desired ticket?" giving one the option of creating a new card because the system cannot determine whether you are traveling within Paris or to an airport during validation. Interesting. Also, I wonder if there is some kind of interconnection between the apps? It would be nice if someone could clearly and simply explain the best Paris transit app to use and how not to encounter the bizarre experiences we have had.

Thank you, Michael