Yes, with such a module you can teach Home Assistant to communicate with HomeMatic devices. Basically it’s like installing a CCU directly on your Home Assistant machine.
Be careful to chose the right module for your devices. The old wireless devices are different from the newer HomeMatic IP ones. Some modules support both variants, some do not. RPI-RF-MOD supports both. So that might be the better choice if you plan to use both types in the future.
Here it says: Kompatibel mit Raspberry 2B, 3 und 3 Model B+
So no, that probably won’t work out of the box. But have a look at this site. There seem to be solutions for Pi4 users.
In general, this is all information you should be able to google yourself. Just give it a try.