Last year I had 2200 or something like that open, but I haven’t counted this year. FF handles it fine. Chrome wasn’t ever able to handle more than a hundred or so. I haven’t used chrome in 6 or 7 years now though.
I don't really understand how bookmarks would help. Like, let's imagine you're in your office doing research and your office happens to be the Library of Congress. You have a bunch of books with different references open on the table. You need to go to sleep. Is it easier to write down every single page you have bookmarked and put it on a piece of paper on the table, then close all the books put them back on the shelf, go to sleep, wake up, and then take all the books back off of the shelf, reference your paper, and open every book again back to those pages to continue working? I very much doubt so. Bookmarks are one of the worst inventions of the browser honestly. They do not accomplish anything they mean to. I use bookmarks for one thing. Pages I visit daily and don't need to remember context in. e.g. github repos. And then I use vimium to navigate to them with fuzzy search. Working projects always stay open and I use Sidebery to maintain groupings.