You can try the WriteRGB as last operator of your chain or in addition to a normal WriteOp. It is very simple and allows only the selection of 3 bands for the 3 RGB channels.
If you only want to have one band you might specify this for all 3 channels.
With pconvert you have more options.
See Export bands as images enmasse - #3 by marpet
In this case you have to write the data first and then convert it to an image, but it gives you more options. Afterwards you can delete the data file.