Need to tow a cargo carrier and two bikes, what should I get?

I have a 2008 Prius and want to convert it for long-distance road trips so my girlfriend and I (6'2" male) can sleep in it.

I plan to put a 4 inch mattress topper in the back, and tow a cargo carrier with a trunk and two bikes. I'm not sure exactly what I need.

I know I can do either 1 1/4 inch or 2 inch hitch, and most people say to do the 1 1/4 inch because a 2 is overkill. Is that still the case if I need to tow bikes as well as a cargo carrier and trunk like this?

I'm trying to find a cargo carrier but from what I'm reading, some of them have an adapter so you can put a bike rack on the other side of the carrier as well, but I'm not sure which ones have that.

Should I get a bike rack that mounts on the trunk of the car instead of trying to attach it to the cargo carrier?

I just bought a Habitent to use in case there's not enough room for me to sleep in the backseat, and also to use while camping when I don't have to worry about being discreet when sleeping in it.

Does anyone have suggestions for what I should get? So far the only thing I've ordered is the Habitent. I need to decide.

1. 1 1/4 or 2 inch hitch?

2. What cargo carrier can I attach two bikes to and also a trunk for luggage, or should I mount the bikes on the car's trunk directly?

3. Is there a better way to do this? I was thinking of doing a roof rack for luggage and putting the bikes behind the car or vice versa, but I've heard mpg gets a lot worse when mounting stuff on the roof.