I use two all the time and three for cookies and anything else that is flat.
I agree with Mimi, as usual. You need to know your ovens. I have convection but I don't always use it because I find the swing in temp (different from temp) is larger.
All ovens, even the pricey ones, have their individual quirks. You need to get to know them. I have three in my bakery and I know every odd thing about not only the oven, but each shelf.
You can bake in an off temp oven with hot and cold spots. Just know what to do. Use an oven thermometer. You don't need a pyrometer. That measures surface temp. You can get a $5.00 oven thermometer. If you want to check that for calibration, use the sugar test. Just google it.
Once you have the calibration under control, set your racks in the middle thirds. Remember, the top of any oven is hotter and even convection is cooler near the vent. If your oven on the bottom shelf, invest in a $25.00 pizza stone and place it on the bottom rack. Now use the next two for baking. Bottoms burning problem solved.
For hot and cold spots, just rotate. Most, not all, baked goods have decent structure established by about 2/3 through the baking time. At this point, you can gently rotate, change shelves, or both.
If your oven swing is too wide (the temp it cuts on and off) this can't be fixed and will ruin your baked goods. All ovens work on a system of on or off. They cut on at a certain temp amd off at a certain temp. Most ovens will work within about a 35 to 40 degree swing. For example, your oven is never really at 350. It will be on until, for example, 365, and cut off. The temp will then fall to 335 and cut back on. It's the average that you are looking for. But if your swing is 380 and then dips to 320, you will usually find an underbaked cake or a sinking middle. A spring loaded thermometer is preferred because it is slow to move and more readily shows the average, which is what you are after.
My suggestion would be to get a roll of cheap sugar cookies at the store, slice them and start playing with your rotations. You want the white cookies because you are looking for the slight differences in color. You will find your oven's quirks very easily and will know what to do to maximize your space.