Cookers

I have been doing research all morning about solar cookers. I am trying to find one that is:
Less expensive/but will last years. I don't want to make one that is always going to need something Like for example the combination solar cooker most of them is telling me that am going to need plastic bags. I don't mind that but I prefer something that is just put the pot and and it is done
The ones I have currently found that I like is the Box cooker or the Combination cooker.
Box cooker it seems that you need to be over the cooker more than the combination one.
But with the combination one you need Bags to cook with (has any one every actually cooked with out bags if so does it come out fully cooked or does it just take longer)
With the box cooker I did notice you can cook more stuff at any given moment has any one heard you can make a Combination cooker cook more than one pot at i time
Curved concentration seem good but it seems like it needs more to work and easier for things to get broken But they do say that it gets hotter than the other ones
Being all that said. let me explain why I want it.
Me and my family wants to live off the grid. To do that I would like to figure out what is the best one to cook with. Or is there any other types of ways that I can cook with out using energy?

The use of an oven cooking bag greatly increases the cooking temp. Many of the ovens that use bags are more portable than those that don' t use them.
A parabolic cooker definitely gets hotter. For me if I were to be using a solar cooker in a permanent location a box type solar oven is what I' d select.

i have a fresnel lens and....

Did you look at earth ovens and the rocket stoves? I think being able to cook with just twigs would be sustainable enough for me. Solar cookers are difficult - you have to reposition them, worry about clouds, etc. I just saw another thing - cooking food by putting it in a well-insulated box! So you'd put the beans or whatever in a pot of water, bring it to a boil, and then quick put it in the box and close it up. Not sure how to tell how long until it's done, I guess that takes experience or a digital thermometer, maybe.

What I use mostly is a cone cooker with oven bags. For a frame of reference a loaf of bread tht fills a 10 inch dutch oven takes about 2 hrs. I roughly double the time it takes to cook a normal recipe when using a solar cone. The temperature is consistently 250 degrees for me. portability is an issue for me so that is why I use a collapsible cone. A box cooker like a "Global Sun Oven" is just too big for me.
The bag keeps cool air off of the cooking vessel. I have cooked when there is snow outside and the use of the bag is essential. In our area we take ours kayaking and can set up the oven at our campsite and have a meal cooking while on the water. No fire is left unattended and when you get back a hot meal is ready. During hunting season a fire is sometimes not allowed in areas and we can do the same thing. Cooking with two pots isn't an issue one on top of the other, chili in the bottom cornbread on top.
Hay box cooking or thermos cooking is another way to decrease energy demands.