My first guess was AppX4hxtad77fbk3jkkeerkrm0ze94wjf3s9 was Edge, but I have it too - along with 2 other 'app*' values and one called GhostHTML* - which leads me to believe they are keys for some of the browsers installed (I have Chrome, FF, Edge, IE, Opera, and Ghost)
AppX4hxtad77fbk3jkkeerkrm0ze94wjf3s9 = Edge (Computer\HKEY_CLASSES_ROOT\AppX4hxtad77fbk3jkkeerkrm0ze94wjf3s9\Application)
Another of mine is an app called Universal Code Editor - it can be used to edit HTML pages - and the 3rd Appx value is Skype.
So... anything beginning with AppX is one of the new Windows apps available in the Store.
Do links work if you set IE or Edge as default?