Just a general question?
How do I make images small enough to load quicker, but still look amazing when zoomed in?
When I export an image as 72dpi and 1000px x 1000px. the files size is 420kb
What is the common file size an image should be?
I'm currently working in Coreldraw and Photoshop
Download irfanview and the RIOT plugin for web export https://www.irfanview.com/64bit.htm
But 420kb are already a lot better than your 2 MB images before. Virtuemart itself has a thumbnailer, this means it automatically creates a thumbnail. But your big slider on the homepage is a joomla slider and so you need to set the correct size yourself.
In vm, when you upload a 2 MB big image, then you see only thumbs, all the time, except when you enlarge the image, then you should see the true image.
If you really need a big image, and medium image and thumbs then you have to modify the template product details layout default_images to use another javascript.
http://photoswipe.com/ is one of the best tool for this case, even on mobile phones, but need full code changes.