As a developer at Brave, and an over 40 with deteriorating eyes, I’m also interested in this topic and helping find solutions.
On a personal level, I find the OS controls for scaling to be pretty good at offering a choice so that all my apps have similarly-sized text, at a size I prefer for a given display. For example, the font-size in the tabs and bookmarks bar is similar to that in Finder on macOS or explorer in Windows. And Windows offers a lot of flexibility for UI scaling settings.
I do appreciate apps that offer a choice of condensed or spacious UIs, and a more customizable UI - and I believe we have some features coming up in that area.
In the meantime it would be good to hear how those OS controls fail to improve the experience in Brave, or if there are places in Brave where the text is much smaller than elsewhere in Brave or your OS (and which OS!)