What is the purpose of the proposed counter? You could install a fold-down counter to the right or left of the pair if there's a wall adjacent. If your dryer's lint screen is like the photo, then a counter will get in the way of cleaning it out every time it is used.

Front loading slready have a top meant to be used as a work surface. Why would you make it eternally difficult to maintain and service just to end up with essentially what you already have?

Besides liking the clean look it will help keep things from falling between, and next to, the washer and dryer.

So are you going to reach under the counter to use the controls and will you even be able to see what you are setting them at? With the counter over the top will you be able to pull the units out if they need to be serviced? Will you be able to pull the dryer out and be able to clean the vent? Will the washer hookups be accessible?

Thanks for info. You can keep things from falling between washer and dryer with gap fillers like these:

https://www.amazon.com/dp/B082Q3SX3M/

As for the sides, there are skinny cabinets that will slide in between wall and appliance. Or install a narrow shelf on the wall, painted to match the wall or painted white to match the washer and dryer.