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Are you sanding off paint or just sanding bare wood. It's common to use a delta sander and a square random orbital type. Festool also do a linear sander which works well. Having only 1 sander is not really a thing, over time you end up with at least 4 or 5 and use a few on most jobs.
One of the most useful I have is the Festool RTS400, if you are looking to have just one sander then this is the one I would choose. A multitool with a delta sanding attachment is useful for the corners. Sharp chisels work well for the corners too.
If they are painted I would recommend stripping the paint rather than sanding it off. Use an IR stripper or chemical stripper.
Cheers. I have neither atm so looking to buy. Assume corners will be an issue with circular RO.