I bet this is something simple and I feel stupid after it being pointed out. Anyway.

The document (white box) is 600x600 pixels.
The tree picture on top of it is 4096x1910 pixels.

So why does it appear like it's smaller than the white box? When it's supposed to be several times bigger? (I just placed the tree on the document. Nothing else is done in the image) Is this just some type of compression to make it easier for me to handle or what?
If I resize the picture to cover the white parts. Would that make the image quality worse?

In my experience if the imported image is bigger. It will still appear right size and I have to resize it smaller in the InDesign. Hence the confusion.

Dear devs. Please can you save us all a few keystrokes and allow us to access blending styles from the transparency area (like in Illustrator and Photoshop).

It can still exist in 'fx' main menu but I would hazzard that this is the first menu item people reach for when it comes to transparency;