True, sometimes the leading leader of warming is methane, which takes a while to turn into more mild CO2
You can test your cloud theory at night, does it stay warmer on a cloudy night or a clear night? Water vapour is actually the biggest green house gas on the Earth, remove the water vapour and temps will be 20C or so colder (might be mis-remembering the actual number)
For plants, CO2 is like sugar for humans, sure it causes more growth, but not good health. Humans get fat, plants get leggy. Both flourish with a balanced diet of different nutrients. People, a combination of proteins, fats, sugars and various micro-nutrients, vitamins and minerals. Plants, CO2, nitrogen, phosphorous, potassium, and various micro-nutrients, from calcium through iron and other minerals. Both people and plants also need oxygen as well.