I think you are absolutely correct about trying a style before you buy it. I borrowed my daughters structured bag before I bought a Zhoe and used it for an afternoon going shopping at the mall. It was fairly similar to the Zhoe in size and style. The other thing I did was make a paper pattern of the bag to get a feel for the size. I cannot judge sizes very well by the measurements. So I stick sheets of paper together because the paper sheets are normally not large enough. Then I measure it all out cut it out and stick it together - just like paperdolls construction when we were kids. I can then tell if the size will work for me or not.Just a word of caution. I cannot tell you the number of bags (and money) that I have wasted buying something "different" from the style I prefer. If possible get a structured bag and carry it (it won't take long) to see if it works for you. IMHO
I also wasted a lot of money on Rebecca Minkoff bags that did not work for me. I bought them and sold them immediately sometimes because the size and structure did not work for me but towards the end because I did not find the quality as good as earlier RM bags.