Is it Important to merge VTX on model?

Hello, I have an model of an Wall wich has several difrent types of brick pattern. On of wich is an Brick Curve above the window. I cutet out such an hole and inserted there my "CurvePlaneMesh",wich perfectly fit’s that hole, and I later polyunited it into one model.Those models are on the same Plane. Do i need to polymerge the VTX for any reason( Lightbuild ) ?

Similar to my problem would be an simplification in wich we put next to each other two “polyPlanes” and polyUnite them without merging the VTX.

Thank You in advance.