"Red conflict" simply means the mods alter the same files, it doesn't mean they'll automatically crash. In the case of the MegaMod, its 3 parts will always show up as red.
The larger the mod, the longer the loading time. Unless you are dropped back to your desktop with an error message, the blackscreen doesn't meana crash, just slow painfull loading. <abbr title="Colonial Charter">CC</abbr> is several times larger than the base game, and MegaMod is again way larger. Depending on your computer the loading time for <abbr title="MegaMod">MM</abbr> can go from just a few seconds (omigosh, I want a computer like that) to what feels like an eternity (14 minutes on my laptop). During that time you can actually alt-tab and go do stuff.
That super long loading time will happen first when you exit the mods menu (the game needs to reload everything). Once you're back on the main menu, you need to exit entirely the game to make sure the modchanges are correctly registered. If you don't, you will crash when trying to exit your town. Restarting the game will again mean a long loading screen (you'd get it anyway if you "enjoyed" a crash, so might as well do things cleanly!), then you can start your new town.
Depending on the type and size of map you picked, map creation/loading times can vary. Large maps with many lakes are slower to load than smaller maps with less water. I think the slowest to load are large marsh maps, because of the amount of tiny lakes.
Using DirectX11 tends to give much faster loading times, but for some people it is less stable and will lead to crashes while playing. DirectX9 is more stable, but the load times are scary.
Oops, j'ai répondu en anglais. Pour une version en français il suffit de crier bien fort, je ferai si nécessaire!
