Someone mentioned motor vehicle traffic as an issue. Really? Cars are few and far between from Loudeac to Brest in my experience. I did the round trip Monday in 2015 and then in 2019, I went to Brest during the day and slept the night there returning in daylight on Tuesday. My only niggle were some of the little paths they throw us on and oncoming headlights either due to misadjustment or poor design. It was brutal to the eyes in 2015 all the way to Tinteniac. But cars? Not really. I had a slight tailwind briefly on some of the descents, I'd pass a velomobile on the climbs and he would roar past me at 70+ mph, rinse and repeat for an hour. That was fun. No cars. Anyway, a good change except the section from Brest back to Carhaix is very hilly. Into Brest, the route comes down the Roc and then goes right over to Landerau into Brest, which is essentially the return route of of Brest in 2019. You return over the famous photo bridge and then take a more southern route back up to Carhaix (not back up the Roc).
I registered in Wave B. Hope not to regret it.