Just my 2c
I am 107kg.. so i dont race but i do train. I am no tech or number geek.
I have a PM on al 3 my bikes, Gravel, Road and mtb. I find that its the only way i can get comparable data over all 3 bikes ASWELL as from my indoor trainer. Being heavier i do rely on power a lot as to not over exert myself on races.
On the race to the sea I had a IF of 1.3 at WP1, 0.97 at WP2. at WP3 i told my wife somewhere i am going to pop as this was not sustainable, low and behold 10km after WP3 i popped so hard i had to walk anything over 8% gradient the rest of the way. Iff i did not have a powermeter i would have assumed i am flying the first 80km and probably blamed my pop on eating or something else, but i had the data infront of me telling me whats happening the whole time.
Structured training is also the only way to go and then you will need a powermeter.
Iff you have anymore questions drop me a message. would gladly tell you how PLEBS incorportate powermeters into my daily cycling life.