Thank you for 4.0RC3.
I have an issue, they mention in the History:
Gallery editing options added: interval, autostart, width & height

Where can I find the now adjust any settings options.

RC3 does add the ability for galleries to have options for interval, autostart, etc. But it's up to each gallery/slideshow plugin to enable the features that make sense. I will be updating plugins I've created to make use of the new features soon. Here's a new one that uses the autostart, height and interval option: Bootstrap Carousel Gallery

Thank you.