Although I’m a fan of PRS guitars, I never ceased to also be a fan of Gibson, especially LPs and SGs. If you had a LP and wanted to complement it with a PRS, I’d say go for the Mira. Since you have a SG and want a PRS complement, I’d say McCarty or a Single Cut 594, but probably a @McCarty.
The neck depth on the McCarty is very similar to my 59 reissue LP. The neck thickness of the 594 is closer to a 58, as Mozzi very accurately characterized. Regarding the body thickness, the McCarty thicker than Custom 22/24, double cut 594 thicker than McCarty, and single cut 594 thicker yet than the double cut 594. However, all have belly carves and are very comfortable. You can easily find a McCarty and a double cut 594 that weigh less than 8 lbs. I actually think that you’d be hard press to find a McCarty that surpass the 8lbs mark. My McCarty and double cut 594 weighs 7 lbs 10 oz and 7 lbs 6 oz respectively (yes my 594 turned out to be lighter). As an SG player you’ll probably find the on average lighter weight on the McCarty and DC 594 more comfortable than the single cut 594, which are normally a bit over 8 lbs, though sub 8 lbs are not unheard of.
My gateway drug to PRS was the McCarty. I had played other PRSi before and really liked them, but it wasn’t until the McCarty that I truly became a fan of PRS guitars. My R9 is still one of my untouchable guitars, but now so is my McCarty and 594, and for that matter my reclaimed redwood fender tele as well. Yes the PRS term system is stable and reliable, but I still prefer a fixed bridge.