Apps Used For Side LoadingBugjaeger (Link): My personal favorite. Good for any ADB related action that you could possibly need for side loading including bundled installation. Do not prefix commands with "adb".
Easy Fire Tools (Link): Basically the same thing as Bugjaeger with a multitude of other features that could be considered useful or useless depending on the user.
Wear Installer (Link): Good app for quickly extracting the companion Wear OS apk from the mobile companion APK since several outdated apps aren't included in the Wear OS Play Store. Can save the APK or install directly on your watch. No command input functions however.
I'd add ADBlink2 to that list. It's a godsend for ADB stuff when wanting to more than use a CMD on pc.