I can only answer about shafts that I have and have played with for a sufficient amount of time:
1. JFlowers SMO 12.5 mm
2. Predator Revo 12.9 mm
3. CueTec Cynergy 12.5 mm
4. Rhino 12.5 mm
The CueTec is nice; it deflects a bit more than the SMO and the Predator and feels very good, but the ferrule is a bit soft, and I don't think it'll last a long time. Already it has a scratch on it, and I have no idea how it got there. I have it in a 3/8x10 joint, and from all the cues with that joint that I have, it feels best on a Carmeli cue.
The Rhino deflects the most out of that list; the fit and finish is not that great either. It has a good price, and it's much better than the cheap Temu shafts, so it is a good starting point to see if CF is for you without breaking the bank. A Raven might be a good alternative at the price point.
I was used to Predator 314-2 shafts, which are 12.75 mm, and 12.5 just felt too thin in my hands, so I got the Revo 12.9 mm, which is a great shaft. The sound is not that great, and it plays closer to the 314-2 shaft than the other CF shafts. I have it in a 5/16x14 joint, and from all my cues with that joint, it feels best on my Jacoby D4, which hits a bit softer than the Schon cues I have, so with the CF shaft, it gets just right when it comes to hit and feel.
The SMO deflects less than all of the above (it's all in small margins, but it's there), feels good, and sounds good. I have it on a JFlowers cue, which I guess is designed better to work with CF shafts than old cues from 20-30 years ago. This has become my main player.
The long pro taper is a bit flexible; I think I like the Revo 12.4 taper better.
I've hit a few balls with a Revo 12.4 and the Mezz Ignite 12.2 mm, but not enough to form a solid opinion.
I liked the Revo 12.4 mm; I think if I had it, it would probably be my favourite.
The Mezz feels nice but deflects more than most of the brands above; it is similar to the Rhino in terms of deflection. I would like to try the new 12.6 mm when it'll come out.