These are smart symbols. In this case, this features is made to enable you to both align them correctly with the edge of the roof, and also allow you to place them as far in/out as you want. So therefore they take two clicks to place, after you click once to place them, you can move your mouse to adjust the position before clicking again to finish the placement.

Actually, the mapping units CC3+ itself uses are just "map units", completely independent of any of the two.

The real problem isn't if the map is in metric or imperial, CC3+ doesn't actually give a damn about that, it is the scaling that is the issue.

If you just use an imperial template and pretend it is meters, everything gets gigantic. For example, if you place down a car in SS3, that car is designed to be about 15 map units long. On an imperial map, that results in a car 15' long, or about 5 meters, but if you treat feet as meters, you have a gigantic 15 meter long car. So, the solution is simply to scale that car by 0.3048 to get it correctly sized, and that is exactly what the metric template do for you, but unfortunately, there are some issues with some of the tools when it comes to handling things that are scaled (connecting symbols for example).

The house drawing tools always place the frill symbols at scale 1, which is why there exist a separate metric scaled chimney symbol, and metric variants of the tools which are use that symbol instead of the imperial sized one.

If the only goal of the map is to produce an image, you can kind of ignore this and just map using the imperial template, and simply change the values on the scale bar in the end. But fudging it this way means that none of the values in CC3+ makes any sense. All measurements will be off, effects sizes doesn't read correctly, and so on. So while it may be fine if you just need the image, it is not fine for future use of the .fcw (Which is why I require all atlas maps to be scaled correctly)

You need to use the right house tools. There are separate house tools for metric (the SS5C m ones) that uses frills that are scaled for metric maps.

These tools should work just as fine on Metric as Imperial overland maps.

I know they don't work as well in small-scale maps as large scale maps though. What is the size of those maps (the dimensions you entered in the new map wizard)?

Also, have you modified the symbol scale from the default value in the map?

In any case, if you are not happy with the distribution after running the tool, simply undo once, as this removes the trees but leaves behind the background polygon, then immediately run the Draw -> Symbols in Area command. This will bring up the dialog with the same setting the tool just used. Then modify the distances in the pattern section, hit ok, and pick the background poly you created with the tool. This will fill it with your new settings. If you still didn't quite like the result, undo once to remove the trees you just placed, and repeat. When you find a setting you like, you can save it (but I recommend NOT saving over the existing setting used by the tool, make your own)

Anything that makes two entities do it by adding both a main entity and the outline. In Sue's first screenshot above, you can see there are two buttons, "Properties", which lets you change the settings for the main entity, and Outline, which lets you change settings for the outline entity (Which doesn't actually have to be an outline, it was just named like that because that was it's initial purpose)

When you are dealing with with and outline entities, just change it both places. Keep in mind that the values were probably just a tad different originally, so keep that difference in your changed versions.