Solar chargers (regulators) are a heart of off-grid systems. The main feature of solar chargers is to connect PV modules with a battery pack to provide effective transfer of energy harvested by PV modules into your battery. Same time, those charges keep monitor your battery and adjust the energy flow in and out of it to keep your battery healthy. Generally, it means to manage input and output voltage and current.
The main technological difference between MPPT and PWM is efficiency of the charger. MTTP are much more efficient but PWM chargers are cheaper.
Choose based on your preferences.