My 2 cents.
Used to race bikes. Lot's of miles traveling for training and racing over the years. Hauled very expensive bikes around, and used a similar bike rack for quite a while.
Regarding the cover for the bikes. We have tried, and quit using during travel. Wind making it flap can cause issues, and if it's raining then dirt, water & grime seem to find a way to get all over the bikes anyway. There is nothing better than a little soap & water for the bike after a dusty or wet drive. Just don't use a power sprayer.
A good lube on the chain, frequently if you're riding on the trails, will save you a lot of heartache. Read a lot of studies on the different lubes over the past 25 years. I settled on Rock-N-Roll lube (Rock"N"Roll Lubrication - Homepage
) because it actually does have some cleaning characteristics also. It lasts quite well and you won't have any rust issues.