I can't tell why the imported title blocks come with different scale. Something must be different. Did you notice you can set a factor when inserting at the Tool Options bar? Maybe the reason is to be found there. If not you best provide sample files here. The Imgur link doesn't work for me.
Line thickness out of the box is "By Layer", and out of the box in Layer Attributes it's 0.00 mm. That is shown on screen one pixel wide, but printed it is nearly or totally unvisible.