For the file size, make sure to convert all the images to .webp, it’s a way more storage efficient file format than .png even with a lossless conversion. With a 90% lossy conversion (meaning 90% of the original image is preserved) you can cut the file size by ~90% (those numbers lining up is just a coincidence lol). The lossy conversion is also basically impossible to tell the difference between unless you’re really looking for it and you have the original to compare against, so image quality isn’t a concern here.
For an example of this, check out what I did for Appetite for Growth.