What's better for performance on mobile?

What’s better: one but big mesh or many little meshes?
I’m currently optimizing my Android project, all livhtnili is static. In scene I have flat and interior inside. No same meshes, every mesh is unique. But many of them uses same materials (for example in kitchen interior all tables uses same wood material), so would it be better to combine it for decreasing drawcalls? I’m planning to combine interior in evety room (one room = one big interior mesh), will it work faster or I’m just wasting my time?

It depends on the situation, if the meshes are very simple then it’s better to combine them where you can.

Combine them if they’re in the same area and use the same material and they aren’t that complex.
Just remember though, you can only have one lightmap for an object so if you combine too much then you won’t be able to get enough detail in the lightmap.