The delay depends on a lot of things, from configurable settings for the streamer (both on twitch and on their machine) and for the viewer (low-latency mode, and sometimes, explicitly not! using it), as well as things outside of their control - in Twitch's infra and just general internet latency.
It's not uncommon for streamers to display their chat in a sidebar on the stream, or overlaid on the content itself. From this, I've observed delays as low as (or maybe a bit lower than) a second, and as high as 30s - though I haven't seen anything nearly that high in a long time.
I suspect bigger or more successful streamers are prioritized on Twitch's backend. But I think the threshold for "successful" is actually rather low - someone consistently getting just hundreds of viewers is probably there already, in that top percentile.
Like others said, it depends -- if you have low latency streaming on as a streamer + low-latency viewing by the viewer + good enough internet, your "latency to broadcaster" can drop to 1 point something.
What you linked is streamers intentionally increasing their delay to account for stream sniping, but many streamers keep their delay not-extended to allow for better chat interaction. In some games, increasing delay to prevent sniping is just ineffective -- Valorant can regularly have 5+ minute queues in top ranks, and there's few enough players that even if you enter the queue very late, you can still run into them.
It's not uncommon for streamers to display their chat in a sidebar on the stream, or overlaid on the content itself. From this, I've observed delays as low as (or maybe a bit lower than) a second, and as high as 30s - though I haven't seen anything nearly that high in a long time.
I suspect bigger or more successful streamers are prioritized on Twitch's backend. But I think the threshold for "successful" is actually rather low - someone consistently getting just hundreds of viewers is probably there already, in that top percentile.