OpenEmu is the most user-friendly option for Mac users.
Name: Knuckles' Covert Installer (KCI)
Concept:
A runtime patching system embedded into a modified Sonic3K.bin file that detects when the game is launched and dynamically “installs” Knuckles as a playable character in Sonic 3 (standalone) without needing the full Sonic 3 & Knuckles lock-on technology. It goes beyond simple ROM hacking by leveraging unused bytes in the save RAM to trick the game into thinking the lock-on cartridge is present. sonic knuckles wsonic3bin file install
Android emulation is excellent for on-the-go play. OpenEmu is the most user-friendly option for Mac users