Tilemap questions

I have 2 question regarding tilemaps

i have a project with 2 tilemaps object, and they both have the same image, does this effect performance or size? something i noticed when looking at the sprite atlases generated by construct 3 the tilemap image appears twice even though its the same image unless i loaded the image image incorrectly? if the image is big enough it creates a second atlas page.

another question i have is about which is better for performance? have many small tilemaps or have one large tilemap, ex.. i have sprite sheets for floors / walls / objects, they are separate images would it be better to have 3 tilemaps one for each image? or should i combine all those image and just have 1 large tilemap, that contains all the tiles from the 3 spritesheets, now i understand if the sprite sheets are small it might make sense to combine them but what if each spritesheet is like 1024x1024? would it make sense to have an image 3072x3072 ?

**note none of the tile will have any collisions

C3 doesn't know that the image for the two object types is the same. So it makes space for the image of each one when it's building sprite sheets.

Why were you doing that? Just messing around? Or are you doing something that depends on it?

If you just want to have many Tilemaps with the same image, I think it would be better to create many instances of the same object type, instead of creating many object types.