The best suggestion here is to convert images to the WebP format. It is an image format created and used by Google. So it is a great option to use this format if you want to improve the website speed and get to a higher SERP position.
The extension to use for this I would suggest the Magento 2 WebP Images. It has the 4 conversion mode option that allows you to choose from manual to automatic conversion. Besides, you can set different image quality by which the size of the images will vary. So you can kind of define the speed of your website loading yourself ( by setting certain quality).