The metered fare should be around 95 RMB to 120 RMB pending which location you are heading to and to which the fares on the website are on the higher end of the estimates. I paid something like 110-120 RMB (including highway toll charges) to Tianhe Area. No extra charges for taxi services after midnight.
Some taxis have a bigger boot area and allows for more luggages. They are visibly distinct and could be spotted fairly easily.
Most drivers are familiar with hotels around Guangzhou and should not have a problem getting you there.
However, there are new drivers too. On my last leg to the Airport, the inexperienced driver wasn't sure how to get there and make an earlier exit on the Airport Expressway. That expressway leads right up to the Airport and terminates there.

