It would probably be like this. In the flats, provided they kept in the peloton, they would easily keep up, and use less energy than an upright. Going uphill, they would move the end the back, even lose it, especially on long climbs like Alpe de Huez. But on similar long descents, they'd pull out and quickly move the front and watch the pack get smaller in their mirrors.
To see how they would be in a pro peloton is an apple to oranges comparison.
When I look at my strava rides and compare my rides between my bent and my upright, I find with the upright, my speeds are pretty consistent. Basically, the differences between my slowest speeds and fastest speeds aren't near as drastic as they are on my recumbent. With the bent, while my overall speeds are about 1-2mph faster than my upright, the differences between my slowest speeds and fastest speeds are far greater with the bent than my upright, all based if I'm climbing or descending. And as I said, on flats, I'm usually 1-2mph faster than my upright.
So, it would be hard to plug those numbers into a peloton. I'd probably find myself moving to the front or to the back based on the grade.

Then again, I'm in no shape for any peloton, unless the peloton is made up of middle aged, pudgy beer drinkers.

As far as handling goes, at speeds 5mph or faster, I'm just as capable on either bike. I can take turns faster on the bent, simply due to larger tires and lower center of gravity. But at slower speeds, 5mph or lower, I need more room to make 90' turns. And at 2.5mph, I'll fall over. With my upright, I can nearly barely move at all and still stay on the bike. I can also take sharper turns slower too.
But on either bike, a good gust of wind will affect me equally.
After riding the bent for more than two years now, I'm comfortable on either bike as far as handling goes.