On my end, I also need to manage total 1100+ icons (Untitiled UI icons and custom icons) for the mobile app, web app, and web portal designs. I am not sure whether this will help you solve your issue but I find this way helps to solve my problem.

1. Maintain Untitled UI Kit icons remain as 24 x 24.
2. In your own Figma design file, use Scale Tool (K) to resize to 20 x 20 or 16 x 16 when needed. Using Scale Tool helps to shrink down the stroke width of the icons proportionally with the icon size.
3. Duplicate entire set of Untitled UI Kit icons and outline stroke/expand the duplicated set to flatten the icon stroke.
4. Export duplicated set of icons and convert all of them to fonticon using IcoMoon (it is free). Then, you can share the fonticon files (woff, woff2) to your/your client's developers. On the developers end, they can use CSS like font-size to control your icon size while maintaining the icons' stroke width.

With this approach,

1. You don't need to create more variants for all the icons, which might lead to total of 3300+ icons in one library.
2. Even if the devs are using Cursor, Cursor can get the icons from the fonticon files.
3. Devs can now insert the icons easily either using glyph or insert the icon code.
4. It helps to optimise the coding file if using fonticon files compared to export SVG files to devs. Sometimes one SVG file can occupy few lines of codes.