> How many columns/rows can you realistically fit in screen?

I don't know why you think many rows is an indication that you're editing. Tables are the first resort for reports, and reports tend to have lots of data (i.e., rows).

While I'm not a fan of horizontal scrollbars, I absolutely prefer to render thousands of rows with a vertical scrollbar than use pagination. Give me a sort key or two, a filter box, and I'll whittle it down to what I'm interested in.

I've seen Airtable show up on some sites lately, and its scrolling performance is abysmal. None of the examples for Grid.js has more than a handful or rows, so I won't take its performance on faith. So far, DataTables has been my go-to option for web tables, but I'd happily switch to something else if it performed as well.