Thank you for contacting us and I'd be happy to assist.
Your observation is correct and at the moment, the Toolset's Gallery block doesn't include the option to limit the number of images or the support for lazy loading.
We have internal tickets to introduce these features and though I don't have a time estimate, I've added your voice for these feature requests too.
Thanks for confirming this. It's crazy a system that's as developed as Toolset does not have some form of lazy loading either in its sliders of galleries.
I saw a post recently by Dario where blocks are having some new performance features added.
Fortunately when the Gallery is used in Blocks, WP's native lazy load kicks in otherwise it would make this unusable considering performance is about to become all the more important.