2" Hitch Receiver for 2011

I have spent a lot of time on Prius Chat today,but nobody seems to have asked this question before. I have a 2011 Gen 3 Prius. All the hitches made for that (Curt / Draw Tite) and sold by retailers like E-Trailer, SuspensionConnection, UHaul, etc. have Class 1 hitches with a 1.25 inch square receiver.

If I want to attach a cargo tray or an REI Cargo box - both of which need a 2" receiver, can I just get an adapter to go from a 1.25" receiver to a 2" receiver or is that not available / not possible / not recommended?

I am going to be carrying at the most 100 lbs on the cargo carrier. A Class I hitch with a tongue weight of 200 lbs along with an adapter, should be fine for that, right?

The TorkLift Central's EcoHitch has a 2" receiver, but it is almost 2.5 times the price of a Curt hitch and more importantly, they won't be able to deliver it to me before I leave on my cross country trip. So, that is out of the question.

Extra credit questions:

1) Can anybody give me an insight as to why something like the "Thule Transporter - Combi Hitch" at REI would need a class 2 hitch if the box can only hold a max weight of 165 lbs (well below the rated tongue weight of 200 lbs)? Especially when people are doing stuff like pulling big trailers / boats / cars behind Priuses. You can find all these on YouTube. I am a newbie and this forum doesn't allow me to post links.

2) If anybody here has any insight on what kinds of hitches these Priuses pulliing a trailer/boar could be using, I would love to hear back from you.

3) If possible I would love to get a micro trailer from SportsRig pulled by my Gen 3 2011, Prius III using a Class I Curt trailer hitch. The micro trailer is only 180 lbs. Hopefully, the collective wisdom in this forum can tell me if I can do it or not.

(Sorry, I am a new member and can't have links in my posts.)