If you had to settle with ONE NONPREMIUM bullet weight for 35 Whelen for shooting targets and thin skinned critters out to 300m or so what would that bullet and weight be? The Idea is get the closes to optimum performance for me with buying the fewest boxes of different bullets, something that yields the best compromise between terminal and ballistic performance
Well, I'll throw my 2 cents in.
I know what you are asking and seeking, but you set some limits which I would not do for myself. I believe you can use just about any bullet of appropriate weight and get the job done on game animals, if you limit yourself in certain situations. Limiting to just one bullet will be one of many of your compromises, and only but a few cases, be ideal or optimum. A 225 gr Nosler BT would likely take care of 90-95% of your needs in that cartridge. But it's that 5% scenario, which is what I plan for even if I don't need it. And that's why I use premium bullets. Then I shoot which ever one shoots best.
When you use words like ideal, optimum, and compromise, it makes for tough decisions. Specially when you are compromising right from the start.
I would suggest at least 2 bullets, one for plinking and practice, and one for hunting. And shoot enough of the later, as to know what it's doing.
Punching paper is one thing, but hunting is another. The cost of hunting can be costly, specially if travel is involved. And if it isn't, I don't let the cost of the bullet become a factor either way. It is what finishes the job for all my efforts, I might as well use the best for the task at hand.