Question about Performance (For model exported from Blender)

Unity Engine
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1

I was wondering what would be more effective for performance?
So, I made a model in Blender, I made it like this,
I’m talking about the middle box like part.

Imgur

Imgur

I made the small box like elevated surfaces separately. But they share the UV space and same material with other parts of the model.
But I’m thinking that this way, The mesh will be more performance costly as there will be two separate objects.
Will it be better if I just extruded the smaller surfaces from the middle big box itself?
The reason I’m doing it this way if because the UVs become more complex if the details are extruded (modeled) on the main mesh itself and it becomes harder to unwrap them properly for texturing.
Convenience aside, What is better performance-wise?

2

If all parts are joined into same mesh object, then there will be barely any difference for the performance. In both cases, all program sees is the list of vertices and another list of 3-item sub lists that determines which vertices are connected by faces. Option 2 will actually generate even more faces which is worse

3

Ah, Right. I should have thought this before.
The thing is I’ve been modelling by option 2 since I started (5 months).
Seems I’ve been doing it wrong all this time

Thanks for the help btw!