It sounds like you're moving around a lot. You may choose to purchase an actual "cargo trailer". Also one that is covered, although some people use rubbermaid bins in the trailers.

Personally, I do use my backpack or trailer more than the rack. Plus, I only have a rack on a couple of my bikes. But, the rack is good for touring, and carrying some things.

Locks depend on the environment, and how much of a target you think your bike and gear will be.

I've used a cable lock off and on, but after seeing cut remnants of locks near where I was locking my bike, I went back to a more modern U-Lock. Right now I've been using a Kryptonite NY lock. It is beastly heavy, but would be a major theft deterrent. Generally, I only lock one wheel and the frame unless I consider there to be a particular increased risk. My last tour, I decided to just bring a cable lock with me as I didn't expect to be leaving the bike very frequently and it was half the weight.