Ventilation

[Sargan]

Green house ventilation ...
I bought a second hand EDEN 8’ x 12’ ... just assembled it on weekend.
Couple of questions on ventilation ....
It has 2 x 24” square window vents, and that was all the previous owner had in place.
I also have the Louvre vent, which has never been fitted .... (but no glass)

Is it worth fitting a Louvre vent ? .... I guess if I do, it would not make any difference whether fitted on rear or side ?

Secondly is it worth buying the automatic window openers ? .... and if so, anybody got a view on which ones ....
Greenhouse Spares Autovents at Gardencraft, Porthmadog, Gwynedd, North Wales

They range from £18 to £40 ... all fit same size windows ... so are the more expensive spring ones better ?

Do I need to fit one on each window ? (not intending to fit to Louvre)