Sry I don´t have any tips how to deal with the scale. As far as I know the scale of the MB Models are 1:10 and this have a special reason and there is no chance to scale it down.
Scrubs mentions the scaling factor somewhere and advises not to scale down the models. I can live well with it and have no problems with it so far. If you import models from bricklink into blender then the meshes must be scaled up by a factor of 10.
What do you mean that Blender has performance issues?

greetings and cheerz

Thank you for letting me know. My desktop is running an rx 570 and it can get pretty slow when viewing things in rendered view. I suppose I just need to figure out render layers in blender lmao

Hm I do not know how renderlayers should improve the rendered viewport. I have rtx 2080ti and have also problems with the viewport especially with big scene setup or a massive lightning setup. Of course the denoised viewport is really a godlike present for me and improves my workflow dramatically. Im working with layers but not renderlayers. for instance when I lightning a floor of an interior I set the rest of the interior to indirect light. This speeds up the viewport also.