I used to do triathlon and am coming back after a bit of a break!
I have a perfectly good road bike with clip ons and have promised myself I am not going to get a tt bike until I have at least one or two seasons of racing. I have a smart turbo and do lots of my riding on zwift and have got used to using ftp and power to gauge my efforts!
I have been given permission by my wife aka chief financial officer, that I can make one big upgrade to my bike as my Christmas present! I have been looking at lots of any bits and pieces, but am considering a power meter, probably a power tap set of wheels, so I can swap them if I do ever get a nicer bike! Is that a sensible idea? My budget is not amazing and a Powertap would consume pretty much all of it! I am thinking of doing middle distance/long distance as I enjoy those much more that the pain of sprint and olympic!!
Power meter is the way to go. If I were you, and wanted to have an easily transferable power meter, I would look at pedal based power. Powertap and Garmin both have solid products. If you are looking at getting race wheels down the road you will still have race day power, and you can use them on the turbo as well to keep a consistent metric both on and off the turbo.
A PM and the dedication to getting the best out of it. You’re already half way there with the smart trainer. A PM will help with pacing as well as training.
Powertap is a great PM. Get a good build and you’re sorted. Something like a Flo 60 rim and there’s little reason to get anything ‘better’. (Tell your other half that it’s spending to save later).