It depends on the style and type of oven…not the sun. As long as you have bright sun…the oven is the constraint.
Now, you might know, I spend a lot of time (weeks) way out in the desert. Everything I have is portable. (I’ll show pictures). So, my solar oven for one folds up to about 6” square and tucks onto a little bag. The full sized ovens are not portable…big black boxes with fold out silver reflectors…about 3’ square and stand about 18” tall. They can cook up to 400. My little flexible all sliver oven tops out at 275… no matter where I am.
As for plastic taste…that is what she was cooking in. I have 3 different black metal pans. Depending on what I am cooking and how much. No plastic comes in contact with the food.