I don't think strategies for doing away rotations and procuring letters and interviews are particularly generalizable.
You should probably have a reasonable idea at this point of how adept you are at making a good impression on people. I think it's a leeeeetle bit aggressive to strategize a way to "stand out among your peers." You're read it a million times on this forum; be nice, work hard, try to get involved in research.
Whether you go with GFunk's plan #1 or plan #2, there's a vast amount of variability (and like Neuronix said, plain old luck!) in how things could pan out. You never know when you're going to hit if off with an attending (although you increase your chances if you are nice, work hard, try to get involved in research). Even then, you don't know if that attending is going to be the type who takes the time to write an individualized LOR, regardless of how much you "stood out." If you go with #2 - the 'attainable reach' - there's no way of predicting your chances of matching there, which will be based on far more than your performance during your rotation (other applicants who have multiple graduate degrees and cured a few cancers and have a 290 on step I, attendings you didn't work with who don't like the way your eyelashes curl, etc.).
Of course even after you get an LOR saying you are the most stupendiculous rad onc rotating M4 ever and you practically cured a sarcoma just by talking, there's still going to be programs that you think will offer you an interview that won't...and you'll never know why.
As far as regional bias goes, I can only give my n=1, anecdotal, experience (which you can smush together with all the others). Spent my entire life in the midwest including undergrad, med school, rotated out east and in the midwest. Had 2 interview offers in Cali (of 3 I applied to), about half a dozen in the midwest and east coast each, 2 in the rockies. Only applied to two places in the South/Southeast (I don't deal well with humidity) and went 1/2 there. I think it's totally 100% random. That said, you can hedge your bets by "diversifying" like GFunk suggested. Either coast would work; just demonstrate your willingness to change locations. Or come to the midwest (I still haven't figured out why so many people deem it so "undesirable." I think it's jealousy)
Aside from letters, there's a couple of other very valuable (and underrated on this forum) things I got from my away rotations 1. An understanding the key differences between rad onc programs, and how much things like size, didactics, role in tumor boards, research opportunities, clinical volume > reputation, etc. meant to me when I applied and made my rank list 2. The friends I made (If anything "stood out" at my big cancer center rotation, it was probably how well the co-rotators all got along) 3. A solid rad onc learning experience (the alleged goal of a any rotation...)
Rotate where you want to, not where you feel like you have to. Be the change