It’s the legs and lungs that determine the speed, not the bike. For an average leisure cyclist I don’t think weight or bike frame matter so long as you are comfortable. I see have seen people on the hills round here that my kids refer to as coffin dodgers and I am glad I am in a car and not cycling because Christ they can shift up those inclines.I have a carbon cannondale synapse that I will be looking to sell around spring time.
It’s a good comfy bike iv just had my eyes swayed by something else. I wouldn’t rule out the endurance bikes thinking their slow I’m not a great cyclists but have a lot of decent times on Strava, a friend has an sworks and I’m considerably quicker and follow a few keen cyclists and they aren’t to far ahead so the bike is more than fast enough