The simple answer to Gserve's question is that since 10-2 wiring is installed by the unit's manufacturer, NEC 310-16 states the maximum overcurrent protection for #10 wiring is 30 amps. So, presuming the NEC applies in a mobile home, a 30 amp CB is the max size permissable to protect the wiring, a 20 amp would be OK (no violation) but may produce neusance tripping during operation of the cooktop. Installing a 40 amp CB would be a violation.
As far as the cooktop being a continuous load goes, I believe it would be considered continuous because it could potentially be on for a period of 3 hours or more. No one would really do that, of course, but there is nothing inherant to prevent it, like a timeout interlock or some such device. But regardless, all this is beside the point of the question asked, which was what size CB to use.
Sorry to have gotten off track,
There are 10 types of people. Those who know binary, and those who don't.