I struggled with the exact same issue last year. I was trying to decide between Roll-N-Lock Truck Covers USA, and Retrax Pro. Like you, I did not want to give up a lot of space in my truck bed to a canister. I finally decided on the Roll-N-Lock. Here's why. Roll-N-Lock has one of the smallest canisters on the market. It's only 7 1/4" high x 9" deep. It looks good and is reliable. I wasn't too thrilled about the strap at first, but it has grown on me and I don't mind it so much now. My biggest complaint is that it leaks (especially in the corners) more than I would like.
I looked seriously at Truck Covers USA's American Roll Cover as well. Their canister is one of the smallest as well at 8" x 8" and they're American made. I decided against the American Roll Cover for 2 reasons. 1. You must remove the grab handle in the back of the truck in order to install the cover. 2. You are supposed to drill 2 more holes in your truck for drains and I didn't want to do that either.
I also looked at the Retrax Pro. The Retrax Pro is really popular with many truck owners around where I live. I really liked its looks and the way the cover works and locks, however, they have one of the largest canisters on the market. It's 12" x 12". I just couldn't bring myself to put a canister that big in the back of my truck. I have spoken with several owners of Retrax Pros and have mixed reviews on how well it keeps water out. Some say they hardly get a drop of water in the bed of their truck, while others said theirs leaks like a sieve.
There is a fourth cover you might want to look into- the BAK Revolver X4s. There is no canister, so it doesn't take up any space in the bed of your truck. I have read that it does a good job of keeping the water out as well. I didn't choose the Revolver X4s because I was looking for an all-aluminum cover. The X4s is vinyl covered aluminum. Also, the X4s is either completely open, or completely closed. You can't open part way like the other covers.
AMP Research retractable steps were one of the first things I installed on my '21 Sierra 1500 AT4. They work well and have been very reliable so far. AMP has several different models available. The PowerStep is the basic model and the one I have. I have been very happy with it and it works exactly the way I need it too. The PowerStep Smart Series allows you to operate the steps and lights independently via their app if you want to. The PowerStepXL drops down 3" lower than the basic Power Step. The XL is marketed towards trucks that are lifted. Finally, the PowerStep Xtreme is for those whose truck operate in extreme and challenging conditions. It comes with 2 motors on each side to operate the steps. I don't think it is wet weather you need to worry about. It's more snowy and icy conditions that should concern you. My biggest complaint about AMP Research is that they don't offer a wheel-to-wheel model.
This got a little longer than I originally intended, but I hope it helps. Good luck and let me know if you have any other questions.