The reason Scale is grayed out in LayOut is that you have the camera set to Perspective for the scene in SketchUp. Change the camera to Parallel Projection and update the scene. Then send to LO or update the reference in your existing LO file if you still have it.Make sure the scene has not been modified in LayOut. Look at the SketchUp Model panel with the viewport selected.
As for the paper size when you send to LayOut, are you getting the window giving you the choice of paper sizes? If not, go to Preferences>Startup and make sure Prompt for template is enabled.
Do you want the gray background in the viewport? If not, edit the style. Set the background color to white and turn off the sky. Update the style (click on the thumbnail for the style in the upper left corner of the Styles panel.
Then save the changes, go to LO and update the reference. Turn off Background under the Styles tab if you don’t want any background fill in the viewport.
FWIW, if you have certain things such as paper size, page borders, text blocks, etc. that you always use, it’s a good idea to set up a custom template so you don’t have to set all those things for each project.