Are there more formats that Quicktime can play? Do I need to download additional codecs?
There are other formats QuickTime can play, but you will need additional codecs as specified on the support page provided by Apple. You can use the following link to see what other formats you can play with QuickTime: https://support.apple.com/en-us/HT204382
Additionally, you can install K-Lite Codec Pack or Combined Community Codec Pack to extend the support even further for this player.