CCO, P7, Glock 48, and Sig p239 all fall into the "compact' size range. I own them all, for me they are ideal as the single stack suits my hands better than double stack guns. In the 90's these guns looked tiny compared to full sized guns, but are much bigger than subcompact guns they have available now.
For subcompact, Glock 43 fits the bill if you don't mind quite a bit of barrel sticking out. The magazines come with extended baseplates to improve the grip somewhat as it is quite short. I upgraded to Pierce base plates to increase magazine capacity to 7 rounds. The neat thing is you can put a G48 slide on the G43 to create a CCO like platform. The boberg is very small with no protruding barrel. It's heavier than the Glock 43 with a heavier DAO trigger. That being said it is very accurate and handles recoil better. It does have a proprietary system and the earlier ones released by Boberg requires use of antiseize compound to lubricate barrel and locking lugs. If you use quality ammo it is very reliable and the DAO trigger isn't too bad, I had originally tried a lighter spring to reduce trigger pull but found it made the reset too light so I ended up using stock spring and got used to the heavier pull.
For a person getting into smaller guns I would recommend G48 as it is affordable and VERY slim. I hate Glocks but I like the G48 and G43. I really like the Sig P239 but the extended barrel can be a turn off, just like the G43 if you hate pinocchio barrels. That being said the P239 easily matches the accuracy of even custom 1911 9mm CCO's handbuilt with Barsto barrels. P239 is out of production so pick up spare recoils springs and spare parts while you still can.
P7 is a neat little gun that is no longer in production so spare parts can be hard to get. Many reviewers comment on how accurate they are but I found in my hands its shoots worse than the Sig P239 and CCO style guns. YMMV.
CCO's can be heavy if steel framed. In aluminum frame, cracks might be an issue, but with 9mm and frequent recoil spring changes it should be OK. The ubiquity of 1911 springs and parts make it (and Glock 48) very easy to maintain, (I avoid guns that you can't get parts for now). Accuracy of the 1911 platform is a huge plus. Decades ago I had to go the custom route to get 9mm CCO's...they are now built by many companies, my choice would be the Dan Wesson VIGIL CCO in 9mm for a Aluminum framed one.