JPM Stats: 34 year old, 238lbs, 6'2, large frame, large bone size. Natural stronger pull than push, which influences the curling strength very much. In college 280-285lbs bwt (football lineman) curl around 230's for 5's, or so, than in regular workouts. Slight knee start and backbend. Always been my style.
But so what? I don't consider that curling weight anything special, just a little above average for a experienced lifter. Most BB'ers use moderate weights and endless sets for biceps rather than slapping on some plates and doing a few sets of heavy cheat curls. Getting the idea than cheat curls (or any other form of cheating) is not the way to curl is incorect. Cheating can be an art form when it's not a version of reverse cleans. A very usefull and productive style of training, from time to time, in any workout year. A lot of guy's may really suprise themselves with new progress when switching to a looser and heavier style of curling. BB's, in my view, will work the biceps much better than DB's with regards to a cheat style. But feel free to try both, whichever to your liking.
Inner biceps or outter head biceps, it will depend on what your own personal potentional at birth was. Getting those impressive full double split bicep's is a genetic gift. As are high peaked or flat bicep development. Always can improve those biceps but the muscle inserts/leverage (among other things) will influence the shape in the final run. Good Luck.