I have an interior scene
What is better - should i unwrap the scene and bring in unity or
simply apply textures in 3ds max and get it in unity ??
Why this question came to my mind ?
Reason:: I can apply different types of shaders if i dont unwrap and bring them directly, but then it will consume more of memory.
What should be the size of texture ?
Should it be tga ? or jpg ?
I am targeting web/exe/tabs
Let me know
I don’t dare trying to give an advice on your choice to either use SubMeshes or a UV-unwrap. As long as it’s not a huge set of different materials it shouldn’t cause much of an issue i’d guess, but note that every added SubMeshes will make additional drawcalls for the amount cause by the shader used on that surface.
However, regarding textures;
Unless you’d load them using wwwtexture methods (in that case i’m not sure wether the following is true), however it’s generally best to keep your textures in whatever format is best editable for you, or has the least quality loss.
Why (as also mentioned here: Unity - Manual: Reducing the file size of your build) is because unity will process each and every texture to another format (generally DXT 1 or 5, ETC, PVRTC, RGB, Alpha or RGBA)
Saving a picture in RGBA 32 bit, should be the same result as a 32bit PNG.
The only thing you can define is if and what type of compression (none, DXT, ETC or PVRTC) and general bitdepth.
If you’re interested in the theory, i think reading this page: DXT compression explained - FSDeveloper Wiki can provide some help in understanding DXT compression levels, it’s quite clearly explained!
hope to have been of some help 
its a huge scene, must be minimum 100 different textures