You need to. No store on earth will have all of them handy for you. You need to put them on your feet while you sit at home for a an hour. Also, you’ve got a play with the sizing on these unpadded shoes - for example, in a Shimano XC9 & RX8 45s fit me by common measures, but the fore/aft positioning of the arch curve is better on the 46. The 45s splay my toes after 45min or so (even without insoles)
I should add Fizik and Giro have a nice lineup (as do many others), but I never found them the same value or I didn’t like the finishes. Bontrager’s shoes are a good bang for the buck and have gone up a level.
Specialized shoes - lot of pros cut these.