I’ve tried a few different apps to map the Caps Lock key, including BTT and Karabiner-Elements, and the free Hyperkey app is the one that I find the simplest and most reliable for this purpose. Here are the options provided:
On a related note, the developer of Hyperkey has a paid app called Superkey that incorporates the functionality of Hyperkey. Brett Terpstra referenced Superkey in 843: Bear and Glass Teaches Keyboard Control.