I haven’t checked Wix’s mobile speed recently, so I can’t say for sure, but to be honest, as a site creator, the only real option is to cut down unnecessary content. In my case, as a Japanese user, I also focus on reducing font data.
Beyond that, it’s basically a matter of trying external tools like the ones Website Speedy always suggests whenever this topic comes up. And of course, performance also depends on which country the site is being accessed from, which at that point feels more like an infrastructure issue on Wix’s side.
I imagine that in about ten years, we’ll be living in a world where data transmission speeds are incredibly fast, and when that happens, we’ll probably stop worrying about these nitty-gritty topics. But until then, it would still be nice to enjoy a smoother experience.
One more piece of advice I can give you: when I downloaded the images from your homepage, I noticed they were already in the .avif format. AVIF is the latest image format, offering higher quality and better compression than WebP.
If you weren’t aware of this, then it’s likely Wix is automatically converting them in the background. Not long ago, Wix used to automatically convert to WebP, but it seems they’ve recently switched to converting to AVIF instead. That means there isn’t much point in trying to compress your image data further—the difference from here on out is negligible.
I just did a quick test again, and it’s definitely the case that images added to a page are automatically converted to AVIF. If you upload an AVIF file yourself, it stays as AVIF, of course. However, from what I’ve seen, those uploaded AVIFs often look worse than the originals.
My guess is that Wix is re-encoding them into AVIF again, which increases the file size while actually lowering the quality.
In AVIF conversion, there’s a “quality” parameter—typically a value of around 60 is considered roughly equivalent to WebP at quality 80. My impression is that Wix’s background conversion is running at a higher setting, maybe around quality 80.
As a result, even if you prepare an AVIF at quality 60 and upload it, Wix forces a reconversion, and what ends up on the page is a larger file with reduced quality.
The reason I bring this up is that in your case, it might be even worse: you’re going out of your way to upload WebP files to reduce data size, but Wix is then converting those into AVIF, which could be unnecessarily degrading the quality.
Compared to AVIF, WebP suffers from noticeable quality loss, so in fact, you might get better results by just uploading normal PNGs. That way, Wix could convert them directly into cleaner AVIFs (at something like quality 80) for display on your site.
Since your site deals with jewelry, image quality is especially important, which is why I thought it was worth pointing this out—you may want to re-examine this aspect carefully.
This kind of issue has been raised before: when everything is automatically converted in the background without any option to control it, it can sometimes cause unintended problems.
I really wish Wix would give creators the ability to make that choice themselves. It doesn’t seem like it should be too difficult to implement. 
If you try using Website Speedy and it actually improves the loading speed, please let me know. 
Has anyone faced similar Wix Studio speed issues?
）
. Reading through your message really felt like someone handed me a roadmap I didn’t even know I needed. I’m beyond grateful that you shared all of this knowledge with me, purely out of your own interest, without expecting anything in return. That means so much. 
Let’s tackle your questions step by step: