You are asking a lot, but I believe its possible. First really master your trainer. I mean the fundamentals. I have often seen a flier at the field take off and do a pretty good aerobatic demonstration then come in for landing and the airplane was all over the sky and the landing was a controlled crash. Practice until you can fly a precision pattern around the field, make a precise approach and land close to the runway centerline. Practice flying at full throttle putting the airplane where you want it with little effort, and you never get confused as to orientation.

When you have pretty well mastered the trainer in its present configuration, move the cg a little aft and do it again. If you are actually willing to stay with your trainer until you develop real flying skills you can move up with little difficulty. Don't be hesitent about going back on the buddy box with your second airplane for the first flight or so.

In the ARF category, I have a Great Planes T-6 which is not too difficult to fly. It's the only ARF I've ever assembled, but I just liked the looks. Of course it won't do 3D stuff but it really looks cool in flight, and is just a little more challenging than a trainer to fly. With proper training you should be able to handle it. There is always the Thunder Tiger Lazy Tiger P51. It isn't scale and the engine isn't cowled but it should fly almost like the trainer and the cowling could be modified to improve its appearance.

As to cowling, The easiest is of course the ring cowling like the T-6 since cooling isn't a problem if you have enough exit area. A completely cowled engine can present cooling and accessibility problems that you don't need to deal with until you have considerable experience operating engines. A "semi-cowl" is easy to make and looks good in flight. With the cylinder exposed, cooling is not a problem and you can access the engine for adjustments. I have seen pictures of 4* airplanes with custom cowls that really improve the appearance. The attached picture is of a "semi-cowl" on an aircraft I designed as an example of something other than "cheeks".

Ultimately to get an airplane that looks like you want it to, you will need to build your own and not depend on ARF's.