You should always work in your SKP at 'real size' - so 1cm in the SKP is 1cm in the World and in the OCS [where it has been automatically converted to 'meters' in the export process]. if you want a 1m cube draw it as a 1m cube!
The Texture of a Material applied to a Face can be relocated/scaled [either with the built-in right-click Texture tool, or 3rd party tools like my 'TextureTools' or ThomThom's 'QuadTools' - there are several available from SCF > Plugins Index]. It's best to get the Material's Texture the right size rather than messing on trying to rescale things - see below...***
Applying a Textured Material directly onto a Group or Component-Instance can also give odd results in the OCS as the Face by Face UVmapping is not readily available, unlike when it's applied onto each Face individually.
The original size of the Material's Texture will always be used, adjusted by any scaling etc in each Face's UVmapping info...
If you Scale a selected set of Faces the Textures' 'sizes' remains unchanged and they are simply extended across the Faces as the Faces get bigger.
If you Group the selected set of Faces and Scale that Group then the Textures will Scale with the Group, as if you had used a tool to adjust the UVmapping of each Face individually... i.e. the Texture is a fixed size, and shrinks/grows in size with the Group's rescaling...
***For a 'brick' Texture I would adjust the size of the Image in the SKP's Material Editor until each brick+joints is say 225mmx75mm. Then when I apply it to any Face I can be sure that the brickwork is the right size; all I need to do is slide the Texture across the Face until ends of bricks/joints line up as I want...
Using an oddly sized Texture and trying to adjust its appearance by Scaling a group containing Faces using it is a recipe for confusion and eventually madness