One thing to think about is that smaller monitors with some subs may be more flexible in a smaller room. You can put the monitors where they image best and have the best overall tone. Put the subs where they interact best with the room. Since they’re two very different domains in terms of what’s happening in the room, there is some solid logic to breaking the speakers into more pieces rather than monolithic full frequency towers.
As long as you can EQ levels somehow, there’s no problem with adding speakers with too much bass capacity. At worst it’ll be wasted capacity. I’d be inclined to try to play that room sideways, assuming it’s ergonomically practical, which means some kind of treatment for the rear wall which won’t be far behind your head. I’ve got a 12’ x 20’ room and it’s much better played sideways. I like a wide and open sound stage and it’s hard to get that with only 12 feet. 14 feet is certainly better than 11. Of course if you can you should try it both ways. I’ll confess the bass was better when I played the setup on the 12’ wall. I was getting solid response down to 20 Hz. Now it falls off rapidly at 35 Hz before rising again for a while below 20 Hz. There’s real 5 Hz response, but what good is that with a hole between 20 and 35? It’s not too important to me, not as important as what’s happening up higher.