Excuse me for jumping in, yes there is only one model of DEROS as the base plates are changeable unlike the CEROS, you have to buy a new sander if you want a different size, 77, 125 or 150mm.
I agree with Martin, I would definitely opt for the DEROS over the CEROS as its is more comfortable to use and is actually more efficient at collecting dust as it has a redesigned base plate. it also has a redesigned hose attachment so you don’t need a converter to attache to different manufactures extractors. I would recommend that you get a dedicated extractor as a ‘Henry’ can overheat when used for long periods.
I would also recommend to look at the Festool RTS400 sander for your trim work and for smaller areas. They are both truly great bits of kit and will transform your working practice and the speed that you carry out your prep work.