Sometimes when the network speed is lagging, it will seem that the page is not too optimized, thinking that there is no more content, and after 2 seconds it pops up some more.
Thank you for your report. I moved this post to #feature-requests as it is not a bug.
About your feature requests:
We are already working on the “load more” button solution
I’ve added this request to our development queue. In the initial versions of the infinite scroll, we had a hidden element that could be used to bind a loading animation, but it was causing problems with the different query loop layouts.