Hi vipini,
yes, every html and js code is slowing down a website. Even database queries does this. This plugin’s codes are so lightweight, I can’t imagine, you can “feel” its affects. I mean the difference between a normal page load and a page with my popup could be measured in milliseconds.
Are there any tests, where you measured the difference? This plugin is very well optimised, even the css and js files are already minimised. If you have tested, please share your results with me!
Combining static files are not an issue anymore, if you are using https and http/2. Do you use any cache on your page? That will give your pages a boost not only for my plugin, but for all your page load speed.
So I don’t think my plugin needs optimisation. There are maybe some points, where it can be optimised, but not so much. If your website is loading too slow, this is not because of my plugin, I’m sure.