To start it would be helpful if you could post photos of your curtain tracks. Different tracks have different carriers. Next, you can use whatever type fabric you prefer. If you want room darkening curtains for sleeping & privacy then you can always add it to your fabric as a backing. I believe you can buy it at the fabric store or they also sell it at places like Walmart already packaged, but just use it and cut to your needed size. Typically I believe the curtains would be about 1/2-1" beyond your curtain track at both top & bottom(front window), no overlap for side windows. It depends on whether you have open rails (front curved Window, or closed track, on side windows) They should be pretty simple to make if you have at least a average experience at sewing, just height, width, allowing extra for your seams & pleats. I am using room darkening "Eclipse"curtain panels I bought at Target (they come on many colors, $12.99 each). They come in 2 lengths, I figure I'll get 2-3 panels out of each. This was easier than adding the liner. They are machine washable too. I will just be making simple pleats(2" from top & bottom, about 3-4" apart) to attach my curtain hooks to, which then connect to the carriers. Mine have the plastic wheeled glides that ride along the "I" track, for the curved window. Large eye sliders for the side windows. About the mating sections....yes I believe they usually have velcro. They usually hang pretty tight to the wall with the tracks, but if your worried about it you could add velcro at the side edges to secure to wall, or use snaps.
If you need some advice you can always PM Tammy at "Silver Threads"
Silver Threads Custom RV Curtains - Home
The website has some photos to reference, and you might want to look at the forums photos page for more pics here:
She is a vendor that makes them, and has done so for many forum members. She has given many members helpful advice.
Good luck. Be sure to post photos when you are finished. I hope this all made sense