here is a good quote from an article which I've linked below and I can agree with this on my MTB....
"At the other end of the scale, I find myself running out of gears on long, fast descents. If you want to pedal at over 28mph you have to spin at more than 100rpm in an 11-tooth sprocket. If you want to pedal at over 33mph you're looking at 120rpm, so I find myself just coasting more often than usual. If you're going to ride only on tarmac and unladen you might find many 1X systems under-geared."
I used to hit 36 on some of the longer tarmac downhills near me, 26-28 is the max I do now without my legs going like a cartoon character.... it's certainly not the end of the world on an MTB, but could be for road users....I guess you could have a different cassette on the road wheels to make up for this slightly but you'll still lose at either top or bottom end or both
Full article
here, and the Cube is on there too