I didn't go with the shortest possible grip, and
technically an x/xl grip would be slightly more concealable, but I went with a macro grip chopped down to xl-length to use 12rd magazines. Pro's: it does conceal notably better than the standard macro length (I'm only 5'8 w/ 34in waist), the grip profile w/ medium backstrap and oem curved trigger vs oem flat trigger is as close to perfect length-of-pull as I can ask for, the macro mag release is objectively better than the x/xl mag release without needing to get an aftermarket part (though that's certainly an option), I prefer 1913 rails to Sig's proprietary rail for lights. Con's: gonna be hand-size and shape dependent on whether you get 'the pinch' when doing a mag change, and gotta find someone to do the work. There are two I know of, one a forum member here (RegularJoe58) and the other a redditor (u/GoatNickels)
You
can drop an xl or macro upper on an og 365 lower. People also used to chop down g19's to take g26 magazines. The problem you run into is... the grip itself. You will absolutely conceal better with a 1/2" smaller grip length on the regular 365 vs the x/xl 365 grip length, to say nothing of the nearly inch you save comparing the 365 to the macro grip length. Can you shoot it well enough to matter, though? What limitations are imposed by your hand size? I could never make the g43 work* and that frustrated the **** out of me. For clarity, "making it work" for me means reliably ringing an 8" plate at 25m. Wish I could shoot like HonestOutlaw but that ain't me. The xl length, for me, was the smallest I could go while still being able to use the gun to the degree that I wanted to be able to use it. And for me, I needed that little bit of extra circumference from the macro grip over the oem x/xl grip. You may be able to get away with an xl + wilson grip module and be fine, unless you're married to the 1913 rail like I am.