Can / should you put a 28C tire on a rim with an ETRTO of 622 x 14
There's no issue with running a 28 on this width rim. In the decades of 23mm tires being the norm and virtually all road rims being 13-15mm internal width, many cyclists rode 28s since it's the widest size many such road bikes can take.

32 is also fine. 35 is about where issues with squirmy feel are perceptible.