I notice that if I import an Image into the editor, there is an option to enable MipMap (which will increase the size of the imported image element abit)

What about textures in material slots (like color, normal etc) which are imported to the engine along side of model's material elements. Do they have generated mipmap as default or not ?

I want to know if I have to reduce the size of texture (e.g 2048 x 2084 to 512 x 512) for materials of the LOD1+ of an imported mesh.

Material textures always have mip maps enabled.

Thanks for quick reply. with mip maps enabled, should I create a material with lower resolution texture to increase performance ? is it neccesary ?

No no no, that will only have negative effects.

I suggest trying

D.texMipMin (Byte min );// set/get Texture Minimum MipMap (0..16 , default= 0 ), values bigger than zero indicate lower texture quality (smaller mip maps will be used)

to my knowledge mesh lods atleast disables some detail rendering at certain lod stages away from 0, not sure how mip levels specifically works in this sense.

that is, if rendering of textures even are the performance problems you have to begin with.

not much point in optimizing something to be 2X faster if it only attributes to 0.3% of the total load.

alternatively if you have requirements of alot of dynamic loading/unloading of unique materials very often, is to default mesh to a 0 texture material and do the proper material load in the background. sort of streaming, as I do not know if Titan supports asset streaming in that way.