as a glider pilot, i pay a lot of attention to clouds, both from the ground and up close.
at least on days when rain is not in the forecast, clouds form due to thermals, raising warm damp air from the ground. At some altitude, usually several thousand feet, the air temperature falls to the dew point and a cloud starts to form. These clouds look like the small puffy cloud such as the one in the foreground bottom right of the first photo in the original post. They are unlikely to form in groups, are usually isolated in the sky.
As clouds due to thermals grow, there will be more clouds and their bottoms are much more flat than on top. If there is sufficient thermal activity, clouds will grow tall, and have much more structure, be surrounded by other clouds and look very dramatic. These may become thunderstorms. The only way to see such clouds from the ground is if they are distant and moving toward you. All will start at a distinct altitude, extend upward and the sky behind them will be completely filled with clouds.
So while i am impressed with the artistry i see several inconsistencies when I look at the photos in the original posts,.
In the first photo, i would not expect to see the 4 or 5 clouds bunched together with the rest of the sky clear. I would expect to see many larger clouds, but they are all at the same altitude, and would be scattered in the sky. The shape of these larger clouds would be similar; not small and puffy but broader and flatter. Those in the distance would need to look smaller that the ones closer, and have the proper perspective so that all appear at the same altitude.
it's very common to have blue sky above a behind you, while seeing
scattered (< 50% of the sky) larger clouds moving in from the
distance, all at the same altitude, and stretching to the horizon. In fact, the clouds may form in lines called cloud streets.
I think the second photo, with the clouds less defined, looks much more realistic for those types of clouds, but it appears that they reach the ground (as opposed to getting small, even less defined in the distant). On such days I would expect there to be more haze and less distinct sunlight.
i think the third photo with the puffy clouds is the most realistic, but the clouds appear too close and too close to the ground. I would expect to see only a single isolated cloud, and it would need to be smaller in order to appear at a higher altitude in the distance.
again, i'm very impressed with the artistry. i hope these comments will encourage you to consider what i've said the next time you look at the sky, and help with the realism.