I mean, sure. This is supposed to be a database for everyone 
Fog - I don’t believe that UE4/5 has the ability to cull the volumetric fog. As far as I know the only option is to either adjust the settings in blueprint and have them fade in and out with a trigger, or to use your own custom particles and cull them out with a custom volume. I did a search and found this but it looks like they’re using custom particles. Block Volumetric Fog in a Area
Impossible Collision - I’ve never experienced this. It sounds more like your collision settings on the actor are wrong which is why there’s no collision happening. If you click on the Lit drop down in the viewport and then choose Player Collision it will show whether or not there is a collision mesh. If it just looks like the normal mesh without a texture this means you’re using the Complex as Simple. If this is not the case, can you name a specific asset in one of the free Epic sets that you’re having this issue with? You can copy collision from another mesh so a workaround might be to drop the mesh into an empty scene, use the modeling tools to create a simple collision and then save this as a Static Mesh, then use the auto convex collision generator on it and save it as “TempCollision”. Then open the original static mesh, and with the TempCollision mesh selected in the content browser go to “Collision - Copy Collision from selected static mesh”.
The best example of particle emitters for clouds I’ve seen was in one of Epic’s early demos… I’m trying to remember which one. I’ll get back to you on that.