The overall weight and swing weight of the clubhead aren't as critical as how the shaft flexes in response to your swing. A smoother transition at the top of your swing won't require as much stiffness as the head won't twist as much.
Lighter shafts may not offer as much stiffness as heavier shafts but based on human strength only helps when losing strength or not being as strong as Bryson, Day, or other modern pros with excellent training. The 40-45 g shafts in the TS1 drivers are designed to help older golfers reclaim some of their former speed.

Work with a qualified fitter and don't just buy a set off the rack at a retailer. Being 27 or 72 will impact whether you should be looking for the lightest shafts available.

To each their own on shaft weight preference- lighter typically flies higher. Your tempo plays a big part, guys with a slower unrushed tempo - even at high swing speeds tend to favor heavier shafts. Fast twitch tempo players tend to favor lighter shafts. More weight equals more feel, at least for me - i have a slow tempo, but my driver swing speed is 105-110mph i play a 78g driver shaft and 130g iron shafts, i hit the ball farther with the heavier shafts because my tempo and timing are in better sequence and balance. Too light and i lose sense of where the club is especially in the transition into the downswing.

Jason

I was playing AP1 with Tensei red graphite shafts (Not fitted for) so I went to get fit for some new T300 irons, and Ive gone back to steel shafts. I was amazed that my swing speed for a 7 iron actually went up by 6 miles/hour with 115g Project X LZ 5.5 against the Tensei which I think are around 59g.
So, for me at least, lighter is not faster.

Phil

Jason

Everyone above has pointed out very valid points in response to your question. I will add that as I have gotten older I have moved through the spectrum from my early days of DG s 300's to graphite. And of course those being lighter and softer. My experience has been that since I tend to be a player that wants a response from impact, especially in my hands, I do notice that is lost a bit with light weight shafts. I also have noticed that during a club fitting I still make good contact and get the response I want from a steel shaft, but I realize that over the course of an 18 hole round I may fatigue a bit lets say from 12 or 13 on in. Many not so obvious things to think about as well.