Thanks for the message.
1. I got few warnings about `Maximum number of faces reached` so I end up with 50M. Whether a too large number will affect the scene/memory?
Generally speaking RailClone instances most of the geometry unless is it sliced or deformed, which normally keeps poly counts low. I assume in this case a lot of segments are being cut by the clipping splines, causing the messages. I'm afraid this is unavoidable when a lot of high poly geometry is sliced, unless you use some other trick like using Distance Texture maps for render-time booleans. You can read a little about this here
2. Transforming Vertices and Parsing scene in Corona take a long time to finish. Can anything be done to speed those up or this is due render engine?
I suspect this is due to the high polygon count caused by the clipping. If that's the case there's no way around it I'm afraid. One way to check that this isn't a RailClone specific issue would be to convert the RailClone objects to regular max instances using RailClone Tools, found in the Utilities pane.
3. How to force `gaps` to be parallel and to offset/move those gaps ie. LS1 (see image#2)
The recommendable way would be to set the Geometry - X Size & Y Size to overlap the area, align your RC object as needed (move its transforms) and use the Clipping Area to remove unnecessary parts of the object. Hope that helps.
All the best,