I have never owned a Casita, though I have considered them over the years, driven by the factory, and even sheltered in one during a storm when I was tent camping once. Having said that I think they are interesting little RV's the, these fiberglass egg trailers have not changed much in the last 20+ years, they also tend to retain their value better than most other types of RV's and require less upkeep and maintenance.
Having said that they are certainly closer to the hard sided tent end of the RV spectrum, than they are to the hotel room / apartment replacement end. They are lacking in many ways, the kitchen, bath room, and tankage are all very limited. Typically around 15 gallon fresh water / 15 gallon black water, though some of the larger models offer a 25 gallon fresh water and 32 gallon black water tank, which I consider almost functional. Even here unless you one is attempting to do drastic water conservation, you will be needing to dump and refill every few days. To put this tank size in perspective, a 3 minute shower with a typical RV shower consumes about 6 gallons of water, using a cut off switch, navy shower style you might cut that time down to an effective 2 minutes of water flow.
As to your not a morning person concern, the need to make reservations varies depending on what part of the country and time of year you are dealing with. It seems the biggest problem areas with lack of RV sites are the west coast, Florida, and the north east. For much of the rest of the country it is not that bad, I live in western Louisiana, and for the last couple of years, when I remember I try to check vacancies random area state parks, COE campgrounds, etc. for holiday weekends which have online reservations systems, a few days ahead of the holidays. So far in nearly every one I have checked will have a few vacancies a week or two out, and even on holiday weekends there will be availability, even nearly empty public campgrounds around, perhaps that are less than prime choices, on a less scenic part of a lake, etc.
In the summer of 2017, I took a 4,200 mile 30 day trip from Louisiana to Wyoming and back in order to see Yellowstone, and the big solar eclipse, other than 9 nights around the big tourist areas, and during the eclipse I did not make any advance reservations. (though on 2 or 3 nights I did call and make reservations when available a couple of hours out) On this trip I stayed at a number of first come first serve campgrounds, and was always able to find a spot by stopping 2-3 hours before sunset, once it was nearly the last spot in a popular forest service campground, but I did find a spot. Other places it seemed I nearly had the place to myself, such as a public campground (I use the term loosely), in a small town in Kansas, 14 water and electric sites in a parking lot behind the community building with a self pay drop box $10 per night with a dump station by the exit. I thought I was going to have the place to myself, when I arrived at around 7 pm, but one other guy pulled in after dark, and a 3rd showed up early the next morning before I left.
