I will try to shed some light on your question with my own experiences.

I began serious cycling after having participated in powerlifting for years in the military. I became burned out with lifting and had cycled for my cardio workouts and decided to concentrate on the bike.

At 170lbs (about 78 kilos) I had acheived a 560lb squat and had done sets of reps with over 500lbs in my training (no drugs). This is not too impressive in the serious powerlifting community but actually quite average. However I thought it would allow me to really go fast on my bike.

I learned after trying to apply my stregnth to the pedals that the mass in my quads would become pumped from hard efforts and I could not effectively spin at higher than about 65-70 rpms comfortably. After several years of cycling my leg mass declined with the rest of my body and I became much quicker and efficient on the bike.

I could grind big gears up hills quite well but overall I was slower
when my legs were very large. If you cannot spin comfortably in a 85-95 rpm range you won't do so well if you try riding with truly fast groups. It is difficult to do this when your muscles are so large they engorge with blood and actually become tighter as you pedal harder.

I have gained some weight over the years and now just ride for fitness but I do like to go fast when I go and power without a lot of extra mass is the key. If your legs are like slabs of beef hanging off your body then they will be like riding with weights.
A stong pair of legs that are moderately built sizewise is best in my experience. IE strength to weight ratio is what you want.