I agree
You need the regulator and needle valve. But, if you find a combo that has the solenoid and bubble counter included at the same price, that's fine, that's what I got. I think some units have a lock nut to keep the settings where you put them, mine does not, that would be nice, but I don't have little kids or anyone that might open the cabinet to mess that up.
Solenoid is not needed, I keep it always on except during water change when I power off everything but lights.
Bubble counter is nice, but I can count through the Plantguild reactor if I turn the water pump off. Once the bubble rate is completely stable, the pH should be relatively stable, but for CO2 drawdown during lights on periods.
You also need some thing to tie the tank upright, a velcro strap or shoelace or something fixed to the leg or cabinet.
You might want to get CO2 proof tubing, silicone does leak.