@ElsieD, it turns out that lots of things would fall through the standard Anova racks; I even find that toast does better on the Silpat (doesn't stick). The crosshatch pattern @palo referenced comes from the additional rack, not the original Anova rack (which is like a standard oven rack). The crosshatch rack has 3/8" holes, so blueberries will fall through when partly dried.
5 racks may be too many if you're not planning on doing much dehydrating. From one groove to the next is approximately 1 1/8" to 1 1/4" (the grooves do not have the same shape throughout). Accounting for the thickness of the standard APO rack (3/16" ?), the food has to be cut into 1/2" - 3/4" cubes to fit on 5 racks; though it won't take very long before the food shrinks. The additional rack is thinner.
I regularly use 3 racks when cooking: one for the fish, one for the potatoes, and another for slices of eggplant, etc. I find it simpler to rotate trays when there's only one tray on the rack.
One thing I've found is that @Ann_T's Summer Torte works better with peaches that have been dried for an hour or two, to cut down the moisture; 'course I probably use too much fruit. But this way, the cake is not gummy in the middle.
And it's almost certainly true that because I have the Silpats and extra racks already, then they come in handy.
I'm not sure how well I truly understand how steam roast works, but I will use a Silpat on the racks for some vegetable where I want the food surrounded by steamy air. With the pan at the base of the oven, I don't care about drips. Like @palo says, this method takes the place of the perforated pan.
I haven't bought a baking steel because I have a pizza stone for my regular oven (and a bread machine) and eGullet already makes me want to spend too much money. 😁
Also, it's not necessary to buy these accessories until you determine that you absolutely need one (or two)!
