Road bike recommendations

Well, carbon is mega strong and much stronger than metals in ONE DIRECTION ONLY

Hence my note that if you can expect knocks on storage it's not the best material to use, as if it fails it fails totally and you may end up on your face. Hence touring frames are not made from carbon.

The rest is up for discussion and I never owned a carbon bike, so I can't comment. If you have a safe storage for it, knocks shouldn't be an issue.

But downhill frames are...?

What you're saying, generally is nonsense- plenty of ballistic / military stuff is made from carbon composites these days so clearly it can be made to be strong on more than one axis and strong enough to survive landmines etc.