How far north, how many plants, how many questions… A green house is usefull to prolong the season where it is short, It will hold heat and moisture and that could demand a lot of electric devices to remediate unless you physicaly open and close the greenhouse everyday according to weather. In a hot and dry climate some use the frames to hold shade netting for a while. A greenhouse could be adjusted to make a faster growth environnment than outdoors, in wich case you may have to water more. Growing outdoors is different than in a greenhouse, it might be easier outdoors if its not to cold, if you have grown successfully indoors, you can imagine a green house offers the ability to partly control atmospheric conditions, but will be more prone to extreme temperature variations compared to indoors or outdoors.