Apparently I did not order two sizes of anything, just imagined I had.
Returning the blue mesh top for a larger size but this time actually ordered the larger size.
Did not bother ordering a smaller jacket - Angie, that's the situation I'm in with the larger one (knowing it will stretch a bit so tolerating the shoulder snugness for now). I think the smaller would be unbearably snug.
The MIA boots arrived and while the shoebox shows ECRU in my size, the boots inside are black. So those are getting exchanged, since a quick try-on suggested they might actually work for me.