Dealers will tell you a medium duty Rotary Cutter will cut 2" trees. That is true but the Rotary Cutter will not last long.
I recommend cutting anything 1-3/4" and larger with a chain saw or much safer 20V or 40V reciprocating saw. Trim of all branches and run over with the Rotary Cutter. Bundle 1-3/4" and larger trunks and pull to a burn pile.
There are heavy duty Rotary Cutters but it does not sound like you have enough land to justify the expense of a HD R/C and a heavy, powerful enough tractor to power a HD R/C.
I recommend a Ratchet Rake bucket attachment for pulling out brush, NOT TREES, by the roots.
VIDEO: ratchet rake brush clearing - YouTube
Ratchet Rake will also open land for a small garden.
I have a cat 2, 6 ft rotary cutter already. I will check out that ratchet rake.