Reducing triangles, disconnected geometry and removing loop cut vertices

Hello. I’m doing my first models to some game at Blender 2.79, .x format. Becouse of the nature of the game and its engine i have to keep triangles count as low as possible.
I did base of my model using many loop cuts. I use some addon for displaying measurements, so i keep scale quite realistic.

Everything is single mesh/object. When i use limited dissolve, result is quite good.

I still have too many triangles thanks to mess at windows…that’s extra question at end of the post. Anyway i tried different approach, i duplicated all windows/door faces. When that faces are not connected to rest, i can dissolve building walls into simple squares.

I want to ask about proper terminology here, how do you call that disconnected faces, is it still same mesh, or different one? This looks pretty powerfull, no extra edges to determine position of that faces at wall. When i move that faces little bit in front, i can’t think of any issue that can happen. But i still feel like there has to be some catch at this approach. So in general… is it ok to have disconnected geometry at single object?

Anyway this is good for low poly only, at hipoly i will be cutting holes into walls to insert windows…is there any trick how to make such wall having less triangles than when using limited dissolve?

Extra question, lets call it part two: When i dissolve faces, those vertices from loop cuts still remains. That couse many extra tringles at square window instead of two simple ones. I know i can remove that vertices manually one by one with merging,…but is there any better quicker way?

window_triangle

If you dont extrude the windows, you can just use textures, with or without a bump map.

Duplicated windows in this case cause render problems, gaps, weird shading. Maybe it could be handled, but i would not do it this way.
Extrude the windows and limited dissolve should clean the vertices, if not there is more wrong.

Thing is i can use 512x512 single texture for low poly model. Also low poly models at this game doesn’t use any maps. Thats why i want to keep that window faces, so i get higher resolution at windows. If all side would be single face, those windows would be defined by few pixels…
I think i can get away with that duplicated windows, becouse its only for low poly model which render is very simple in that game. So shading etc should not be an issue, i have to test it.

Yeah, extruding and dissolving clear those vertices, it is definitely faster than merging it. This will help a lot at hipoly model, thank you.