Since you are looking for just the 4 & 5-iron, I would say get the same shaft as the rest of your irons, since it's just a transition and not a driving iron.

I would say if you are looking for a 3-iron or a 2-iron, then maybe a different shaft, as most players would use those as driving irons and might look to get a lighter shaft, maybe graphite. But some keep the 3-iron with the same shaft as well, so it really depends on what you want to do with your set-up.

But again, with the irons you mentioned (4&5), I would keep the same shaft as the rest of the irons, as it will keep a consist feel and set-up.

You would always get fitted, so you know you have the proper yardage gap.

I would get fitted from a Certified Titleist fitter. That way you know exactly what feels good and optimizes your swing. You should get a little more distance from the T-MBs as they are bigger trampoline effect off the face.

I have the TMB 4,5,6 matched with the rest AP2 and all have the PX 6.0. I'm liking the launch characteristics from the different heads with the same shafts

I have the 716 AP2 6-gw and have the TMB 4&5. I have the same shaft in all of mine.

I had the TMB 2 iron but am retooling the top of my bag. I switched to a 19 degree HI hybrid and put in 3-4 in TMB irons with x100 AMT shafts. Great feel/launch and spin with those. I have them all through my irons (716 MB) as well as my Vokey wedges

Ended up getting the 6.0 project x. Thanks guys