Displaying up to 1000 datapoints at once seems like a reasonable limit.

But if the library supports zooming, I highly appreciate it if I can just put my 10,000 to 100,000 datapoints into the library, specify a simple filter function (avg, sum, min, max) and let the library pick the points it wants to display at each zoom level.

Beyond ~100,000 datapoints any filtering is likely better done in the database than on the client. For values below that, Javascript is more than capable.