Can i plant MONEYWORT horizontally?

You can plant it horizontally, but it will probably grow vertically anyway.
May I ask why you want to plant it like that?
With your lighting, it will probably get nice and full and be easily kept low to the substrate without much die back of the lower leaves usually seen with over-shading.
You are supplying pretty good light.

Len

hey when they grow too big just cut the tops off and replant them.. thats how i adjust things.