Frontends & Launchers

Frontend/Launcher	Notes
Pegasus	Free. Fast. Immensely and overwhelmingly theme-able (can be skinned to look and behave exactly like any other frontend, given the time and effort). Open-source and actively in development. An absolute pain to configure, and lacks built-in scraping support. Actively being developed (an official Retroid Handhelds launcher is currently being developed with this frontend).
Dig	Free. Slow. Theme-able. Super easy to configure, and does have built-in scraping. Development has been abandoned and the app is closed-source. Consequently, this will never be able to launch certain emulators like Flycast and the GBA build of Retroarch included on RP2.
RESET	$5. Fast. Not theme-able. Slick and easier than both Pegasus and Dig to configure. Built-in scraping. Actively being developed.
RetroX	$12/year. Fast. Theme-able. The easiest out of all of these to configure, by far. Uses built-in emulator cores, giving you handy universal shortcuts in all of your games. Some systems might be faster in RetroX than on the RP2s pre-installed emulators, while some might be slower. Emulation is less customizable than with other emulators. The subscription covers cloud saves, letting you stay synced across any device you use RetroX on, but its worth noting that internet access is required to open your games. Actively being developed and offers a 5 day free trial.
ClassicBoy	$4. ClassicBoy is an all-in-one emulator that uses RetroArch cores. It supports a variety of consoles, including PlayStation, three Game Boy systems, Nintendo 64, NES, SEGA, and NeoGeo. There are a variety of features. Includes hardware controller support, customizable touch screen controls, audio settings, and save states. The only issue with ClassicBoy is its age. The developer hasn’t updated the app since 2014. It gives you free access to basic functions. Paying the upgrade fee is needed for it to be objectively usable.

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Credit to @ryan86me for the write ups for these