Sounds like you must have been fit for your irons since they are not stock specs. You should do the same for your driver. It's too important a shot as it sets you up on most par 4's and par 5's every round you play. You might be surprised on which head and shaft combo turns out to fit you best. I know I have been surprised several different times when doing a fitting. Good luck and welcome back.

The majority will tell you to get a proper fitting, and yes that is the best option. It's worth the time even if you have to travel a bit, and very educational (fun too).
If that is not an option, see if the person giving you lessons has any variety of shafts you can try out.
If you're set on getting the TSR right away, talk to the golf shop about demos. Even if it costs you a bit for the demo, it's worth it as opposed to spending for a shaft that doesn't work for you. Most reputable golf shops will have your best interest in mind when selecting a shaft, and they like return customers, so they will let you exchange after a round if it doesn't work for you.
Good luck and have some fun.

The HZRDUS Red 6.0 or Tour AD DI 6 S are the stock and stock premium shaft options from Titleist that are high launching. HZRDUS is for aggressive swingers so you may want to look into the Tour AD DI or IZ which are high launch and low spin shafts for more smooth tempos. Also the Mitsubishi Tensei AV RAW Blue or Orange.

Really the only advice to give you is to find a certified fitter and get fit. I took a 6 year hiatus and was blown away at the tech advancements over that time in both equipment and fitting. I’ve never felt more confident with clubs in my hand as I do now knowing I spent the time getting it right before buying.

To answer your question as to why Dale and Barry said get fit, shaft flex is the last step in a fitting. Getting fit outdoors with a a shot monitor, the fitter can find the best head and loft, combined with a shaft that launches at an optimal angle for your speed and ball spin. The flex will be determined to improve dispersion.

Good luck getting the best you.

I carry a 913D2 12* with a 44” Diamana S60+ at A3 and a 16g weight. This and a Bassara 55 both have the best feel but the 60 gives 10 more yards. My son has the 10.5 head and Bassara 55. 44” is good because my ball mark is on the sweet spot. I actually have been using blades 3 years now. I got fitted at Fairway Golf. Because my shafts are 1/2” short, I play 2* upright on the irons. The 910s are 1/2” short and fully upright to keep the swingweight correct. The 816H1 is stock length because the lie angles are 1/2* flat vs 910.