Rectangle - It presets window sizes and assigns them to keystrokes. It’s great to quickly be able to move 2 apps to half a screen each, move them between monitors etc. Shortcat - allows you to basically do anything that you would with the mouse by the keyboard. It’s hard to explain so look it up! It also has a brilliant emoji picker that works so much quicker than the native one.
Guitar player here - there is a trick!
Put your fingers into position and apply minimal but even pressure, then pull your arm back by rotating your shoulder (away from the guitar) and use the strength of your arm instead of your fingers to apply pressure.