@3mm I was kind of at a loss too when I purchased my Smart Effector. Never owned a single E3D product. What I purchased that worked for me (from Filastruder) was:

Cartridge Style Upgrade/Parts that includes the Block, Thermistor and sock.
E3D heat-break v6 1.75mm version.

I can't remember if I bought the heater cartridge at the time or not, but I think I just reused my old one. I was at the point of switching from 12V to 24V too.

I already owned some nozzles that I knew would fit, but if you don't think you do, it might be another thing you need to add.