Thank you very much for that information.
So, to recap and make sure I properly understand its working:
Actually what I should do is to make sure I use the image size I need on specific places.
Meaning if on some part of my website an image is disaplyed at 100x100px and that same image is displayed elsewhere as 450×450 I should actually make sure the requested/needed sizes are served instead of the resized 1920×1080 large image?
I actually already thought that was what I should have done. I misunderstood the functioning of the ?Mw=Xxx&Mh=Xxx part 🙂
Yes, for videos I will link to the preview images served by youtube/vimeo. Youtube I have covered already but vimeo has a different way of serving preview images for the videos which are disaplyed and I do not yet know how I can dynamically show the proper preview with any vimeo video added.
Thanks again for the reply and info!