Indicate if streamer online

Not really, but personal opinion.

If you can do it in your website via templates/prerender, then your frontend/webpage doesn’t have to load, then load from Twitch.

It has it all loaded in one go, from just you. Twitch API could be down, but you have the online status cached on your webserver for example. It’s up to you, but you can’t do it pure front end any more