Is it worth viewing the evidence online first? What should I look for?
You should look for a picture of the vehicle in question crossing the “stop” line whilst the signal is showing red. That’s almost certainly what you will see.
Is there any chance of challenging…
You have nothing to challenge at the moment because all you’ve received is a notice telling you prosecution is being considered and asking you to provide the driver’s details. If the driver does not fancy either of the out-of-court offers which may be made, the only option is to see the charge prosecuted in court.
….based on it being only 1 second into red?
Bearing in mind that the preceding signal (amber) also means “stop” and is displayed for about three seconds, I would suggest that disputing the offence on the basis that it was “only” one second into red will not succeed.
What's the standard penalty (points and fine) if the driver doesn't get the course?
£100 and three points if a fixed penalty if offered. In court, a fine of half a weeks’ net income (capped at £1,000 and reduced by a third for a guilty plea) and a surcharge of 40% of that fine; prosecution costs of £90-ish (guilty plea) or £650 (convicted following a trial) and three points.
Regardless of anything else, you must respond to the request for driver’s details within the 28 days allowed.