I prefer some degree of control over the high cloud textures.
If missions involve flight altitudes that go through this cloud, skies having lots of dense structure are illusion-breaking because the textures become invisible when you're above them, seeing them from the other side. Dense cloud from below, but suddenly nothing from above, is jarring. In such cases, a much subtler, gauzy, cirriform cloud is far better, for this disparity does not call attention to itself in near the same degree.
These denser, opaque high cloud textures are fine enough if flights are confined to altitudes below them. But even then, as an ex weather observer (that's why my handle is WxTech, or weather tech), textures which clearly are images based on lower tropospheric cloud forms do clash. Pictures using large cumulus clouds are particularly egregious. Up there in ice crystal territory, the only clouds having supercooled water droplets that are cumuliform are cirrocumus, whose individual cloudless are pretty small; not huge things of several to tens of degrees in width as seen from sea level.
And all cirriform clouds are not dense enough to blot out the sun, for their thinness is insufficient.
For these reasons I cull the worst offenders of high cloud textures.
To have no high cloud for some maps, you could place that map's folder and its load.ini in your MAPMODS folder in #WAW3. In the _tex folder, place there an all-black, greyscale texture, of small size (256 pixels is fine), and call it something like,
HighCloudsClear.tga
In the map's load.ini, replace the existing HighClouds texture name with this one.
Years ago, for a campaign I hit on the idea of making a bunch of load.ini files. Each load.ini would use a specific high cloud texture. Depending on the weather type set in the mission file, a suitable texture was selected from among clear, scattered/broken/overcast cirrus, cirrostratus, cirrocumulus and a mixed bag. The mission files were then altered to call the relevant load.ini, all named appropriately. Such as, load_bkn_ci.ini, for example.
A further advantage of this approach is this.
The game currently has this stupid quirk, really annoying for this amateur astronomer. If you're playing a campaign on the same map over a run of missions, the moon phase graphic loaded for the first mission in your play session stays unchanged for all subsequent mission you play during that game session. If the Moon is, say, a thin evening crescent for the first mission, until you load a different map it will stay that same thin crescent over days, weeks or months of game time. (You won't suffer this if you play only one campaign mission per game session.)
By loading a differently named load.ini, this tricks the game into treating this as a different map, and the correct Moon phase image will now be loaded.