Hi! I am a very novice Blender user and I’m trying to figure out how I can get rid of all of the loop cuts that I made while building this “hallway” set without the geometry becoming all funky. I’ve tried dissolving edges and faces many times, only for the shape to become different. Attached are some screenshots of what I’ve created. I also have Boolean modifiers operating. I’d like those to become permanent as well, meaning not needing the modifier present.
Next to icons in header, there is a menu represented by a down arrow V.
You can click on V then Apply or use Ctrl A shortcut or use right click menu in outliner to apply modifier, making the change permanent.
You can select edge loops and press Delete or X key to open Delete menu.
Click on Edge Loops item to remove selected ones.
Thank you. When I apply the Boolean modifier, some seem to create diagonal edges, and from what I’ve read, that usually means there is some overlapping geometry. Is there a way to detect this or is there a “merge all” sort of command?
You are always going to have at least some connecting edges. Blender doesn’t allow n-gon faces with a hole cut in them.
Those loopcuts aren’t bad, I wouldn’t worry about them too very much.
Understood. Thanks for clarifying that. I come from a vector background and I’m always merging shapes and making sure things are as minimal as possible. I haven’t used the “shade smooth” option on this yet (was doing that a lot on a tutorial modeling something else). Is that option mandatory or can I get by applying materials without it?
You don’t need to use shade smooth. The additional geometry can be helpful if you ever need to change anything. Texture mapping is also more predictable with some connecting edges.
If it’s not Vertex in the middle of the edge, it doesn’t seem necessary to remove it. 
It is also impossible to remove it completely, leaving it to the minimum where the problem does not occur and removing it.
Mesh modelers internally triangulate all faces.
So if you do get rid or edges that are not needed to form an Ngon you do not really clean up anything. Internally Blender will still have to triangulate the ngon.
Note that both these shapes have 16 verts and 16 triangles even if one has less edges and faces marked. Blender still needs to calculate the triangles.
With some more complex ngons there are different possible ways to triangulate them and if you get rid of edges you loose control of how the ngon is triangulated (control of the edge flow).