A couple of different questions here but everything is related to a photo’s native aspect ratio, comparing that ratio to prints sizes, and cropping decisions.
Part 1, Print Sizes Compared to Aspect Ratios:  Both of my cameras shoot 4:3 (in the largest file sizes), and I really have no experience with 3:2 images.  When I look at a 4:3 and a 3:2 image side-by-side, my brain simply perceives the 4:3 as being the more flexible file size for deriving a wider variety of print sizes.  What say you?
Maybe it’s just the slender appearance of the 3:2 aspect that is tricking the eye?  On one hand I can see that 3:2 aligns nicely with several print sizes (4x6, 8x12, 12x1

.  But what about an 8x10 print … isn’t 8x10 a common print size?  It looks as if my 4:3 file would get cropped much, much less than a 3:2 to get an 8x10 print
Part 2, Deciding Exactly Which Print Sizes to Offer: This may be a two-part question.  I am imagining a scenario where I offered my 4:3 files to be printed.  As the creator I certainly want as much of the original 4:3 image to be printed as possible, or as little cropped away as possible.  But I understand that in almost all cases, something has to be cropped.  So I’m trying to decide which is the best approach to offering multiple print sizes; do I simply offer 
everything that the printer/manufacturer can produce (a long list of examples is below)?  Or should I only offer the print sizes that provides the smallest possible crop?  I would likely exclude any print sizes that were 1:1, 16:9, or anything else that was a significant change from my vision of the scene.  
 

:  This may be a philisophical point but … although I would like to offer a customer as many options as possible, I believe there may be a point where 
too many options leads to an over-tasked decision making process.  Could that lead to a potential customer getting confused and frustrated and simply walking away?
Any ideas you have on this matter would be appreciated!
4x6 
5x5 
5x7 
6x9 
8x8 
5x15 
8x10 
8.5x11 
8x12 
10x10 
9x12 
10x13 
12x12 
10x15 
5x30 
11x14 
10x20 
12x18 
12x24 
16x20 
16x24 
20x20 
20x24 
20x30 
24x36