I don't think Venus can realistically be terraformed.But wouldn't it take a lot to terraform a planet like Venus or Mars?
if you settle the cloud layers, you don't need to terraform. Venus has one of the greatest and perhaps rarest gifts the human race could have received: nearly earth G. Mars cannot never will have that. Mars humans might well develop into a separate species, given time and adaptation.
Mars has close to an Earth time period in terms of hours of the day, but I don't think that's really much of an advantage. If Venus (big if ) has some kind of life , it has to be in the cloud layers. Could it be useful? Most life is. Any attempt to live in that cloud layer would have to do so without causing a threat to the native biome.
By contrast, terraforming Mars is difficult but probably possible. If there is even microbial life on Mars, and I think that's possible, than any attempt to change Mars back to a state close to what it once was, is going to have an irrevocable effect on life there. That gets tricky. Is it going to harm it or restart it? It's like bringing horses back to the Americas. They thrive without megapredators to cull their numbers, but they are not really a pest species, they're just reintroduced after millennia.