I’m not familiar with Nicecast. Does it not allow you to record inside the app?
I use Obs Studio for video streaming and with one click I can record my video while streaming. At the end I drag the .mp4 file into Adobe Audition and mix the audio only with my podcast intro and outro.
Takes me about 5-10 minutes after the show to import, mixdown, upload and publish.
For audio to the stream I am sending Group 1-2 (similar to AUX output) on my Soundcraft Signature 12 MTK into a dedicated audio interface for the live stream (Scarlett 2i2). That way I send the full mix including EQ to the stream.
Is everything running through your mixing desk @David? How are you routing the audio into Nicecast?