There is a big difference in gearing between the Vado 3.0 and Vado 5.0/6.0. The Vado 3.0 has a 40T chain ring while the Vado 5.0/6.0 have the same 48T that all of the previous generation Turbos did. They all have an 11T small sprocket on the rear 10 or 11 speed clusters.
The cadence needed to hit 28 mph on the Vado 3.0 is 97 rpm in the highest (10th) gear (40T-11T) and is 115 rpm in 9th gear. The cadence to cruise at 28 mph on the Vado 5.0/6.0 is just 80 rpm in top (11th) gear (48T-11T) and 96 rpm in 10th gear.
So even if the Brose mid drive on the lesser
Turbo Vado's is set up to handle 28 mph at a cadence of around 100 rpm, the stock gearing on the Vado 2/3/4 bikes is not optimal. Most of us are not professional class athletes, so maintaining a cadence of 100+ rpm is pretty difficult.
OTOH, purchase a larger chainring and you should be able to gear the Vado 3.0 for a more comfortable high speed cruise.
Doug