Yeah I carry everything I need to work with a Topeak rack and trunk bag with fold-out panniers. I guess if I carried a laptop regularly I would have to come up with a different solution, but I don't - I have a high-powered PC at the office and access it remotely from home if need be.

A trailer would add FAR more weight and drag than what I carry on the rack. And the rack by itself is quite light, certainly not enough to make any difference when riding without the trunk bag.