The only seat that guarantees some degree of additional comfort is 1D. There are planes with some great seats in front but it varies based on configuration and they seem to switch planes around a lot and there is no guarantee what configuration you will get.

A normal 20" roller will fit but very tightly. Don't overpack or have big pockets on the bag that sticks out.

Also, this plane seems to land very smoothly every time. Does anyone know why? The actual touchdown is very gentle.