For a 9xxx/10xxx trailer a 250/2500 Gas or diesel will work fine.
If you choose the diesel option your good up to the 12k-14k gross weight range before going over rear axle and OEM 17" E tire load ratings.
You sure don't need a one ton DRW to pull that size trailer. Now if your planing on towing a trailer above 15k-15.5k then the DRW may make more sense.
Engine brake ?? The Ford or GM or Ram diesel doesn't offer a engine brake.
I think you mean a exhaust brake.
All three use a VGT or VVT systems for exhaust braking power through the turbo now. Its OEM on all three and is a Great feature and no need for a conventional exhaust brake.