There is a reason Titleist offers so many shafts, including no upcharge options at fittings. The stock shafts for retail rack sales only fit a relatively small % of golfers. Comparing rack models doesn’t begin to delve into the potential of any OEM’s, not just Titleist.
At 74 and LH, of my full Titleist bag, not one club can be found in the rack models. If there is even a LH in stock. By design and necessity, I get fit for everything.

Currently gaming the T-150's with the 6.0 PX LZ stock shafts. When I got them, I wasn't keen on buying off the rack and fully intended to replace the shafts with some Steel Fiber 110 CW's that I have. Funny enough, when I hit the course before the reshafting ever was to happen, I found the LZ's in that club to be so easy to hit and the playability, for me, was shocking.

I tend to like lighter than 120 shafts too, but these just work. I would tell you if you aren gaming the 100's that you may want to consider the Modus 115 shafts. The 105's are good shafts too, but I think the 115's are like the best of both worlds.

Good luck.

The PX LZ 6.0 shafts are 120g mid-launch as are the Modus 105. The AMT White are billed as the lowest trajectory and lowest spin of all the True Temper shafts. Maybe you should try the Modus 3 to see if that helps with the ball flight? I use Modus 3 120s which are high launch in my T100S and they’re very consistent

AMT White are the lowest launching and spinning shafts made by True Temper. Try the Modus 105, its higher launching and only weights 106.5g.

So I had an opportunity to hit them again today.

T150 5 iron with PX LZ 6.0 was around 8 yards longer than the T100 5 iron with AMT White S300. I would say the 2* of loft difference and shaft accounts for that 8 yards.

My swing speed is way down too from not playing this year. I only have about 5 clubs lying around and would go out and knock it around for a couple of holes every now and then.

It's time to start Stack training for the winter!

Shafts should be fitted properly, but it still has more to do with the club head path/angle/location at impact. It's a combination of many factors. You have to remember that length and weight are HUGE factors as well. I play with a few "gear heads" as we call them, more worried about their equipment than their ability level can handle. Choose wisely! It is fun experimenting though. In the end, I'm always Standard Loft/Length/Lie, basic X version in Project X or KBS. It is cool hitting it the same distances that I did 30 years ago. Technology is awesome!

If you are comparing clubs, you should probably try the same shaft in each head. I dd a fitting a few weeks ago to replace 716MB/CB combo set with Project X 6.0 Flighted shafts. I had done lot of research so was thinking the T150 would be the club to get more forgiveness. Tried AMT S300, PX6.0, Nippon 120s/x and we landed on DG MID 115 x100.
Tried three heads (620CB, T100, T150), I quickly opted out of 620CB as those are too similar to what i had.

Titleist fitter focused on the numbers - getting spin and approach angle in the right window. T100 was ok on numbers on and gave me more consistency and few yards more than my 716CB. I did gain a few yards with the T150 heads but was not as consistent in ball flight, spin nor strike.

Make sure you try the T100 and T150 heads with the same shafts and make sure you pick what is best for your swing and delivery.