We have a countertop convection oven that has a bazillion features and settings, including air fry and dehydrate. We really love it and use it all the time. What I have realized though, is that all the different features that make it seem high tech are nothing more than whether you turn the fan on or off and whether you use the top or bottom element or both.
I don’t recall ever using it without the fan and without both elements on. (Ok, for browning, top only.) It has a crazy long owner’s manual explaining all the complicated steps for using the different functions and presets. We finally just realized all we have to do is turn it on, adjust the temperature and time and hit start. Fan and both elements are on by default, and from air fry to dehydrate, the only real difference is the temperature and the timing.
Our daughter has an actual air fry appliance with a basket you pull out. That seems very limiting for the quantity of food you can put in. Yes, mine takes up more counter space, but it’s a much more useable product. It could replace my large oven completely other than say a turkey or large batches of cookies.
As far as preheating, it is so fast that most of the time I just skip preheating and go straight to cooking.
The dehydrate function is good for a beginner. It only comes with 2 racks, so I bought 2 more racks and some silicone mesh. If I were to get serious about dehydrating, I would invest in an actual dehydrator with a larger capacity. But for someone who doesn’t dehydrate much, this is fine. Better than using the regular oven.
Oh, and apparently “air fry” is really just baking with a fan. If you large oven has a “convection” feature, that’s your air fry setting. You would just need to put the food on a rack of some sort instead of a solid baking sheet. And I always put a sheet of foil below because crumbs or grease will drip.