For Zwift, the wheel circumference setting in the MyETraining app has no impact whatsoever unless you are using speed data transmitted from your trainer and pairing the Turno as a ‘classic trainer’ w/ speed & cadence sensors. Then? You have to use whatever weird ‘virtual’ wheel circumference Elite recommends.
(I just looked it up for the Turno, and it’s your real wheel circumference / 15.34), or ~2105/15.34 = 137.2 mm for a 700c x 25mm tire.)
But… you shouldn’t do this! Because, if you do, then you aren’t using the power data from your trainer to determine your in-Zwift speed. You’re using some approximation of your imaginary rear wheel’s “speed” to arrive at a Zwift-calculated power value in Watts that may (or more likely may not) be a reflection of your actual power output. This is because Zwift is treating your trainer like any ‘dumb’ trainer and applying your speed data to a power curve, and spitting out a power number. If the power curve used is different from your trainer’s actual curve, there’s no hope for accuracy! (e.g. 3000 W )
What you want to do is be sure that you are transmitting POWER data from your trainer to Zwift. You do this by pairing your trainer (or the Misuro B+) as a Power Source - not a speed sensor.
Your in-game speed will then be determined by your power and your weight (in your Zwift profile).