I also connected an audio GD NFB-1 2015 with the Sabre ES9018 directly to i2s input from the kali reclocker, and that sounds perfect in my opinion, I also use the allo isolator.
I also use two pairs of good linear power supplies.
I do not experience any harshness in my system.
for this I had a denon da-300usb / rotel ra-12 apmpiler with dac / Cambridge Audio DacMagic 100 and last but not least the normal cambridge dacMagic, and I think the audio gd NFB-1 2015 with the sabre es9018 sound better.
product audio gd NFB-1 2015 dac: audio-gd.com/Pro/dac/NFB12015/NFB12015EN.htm
here the rj45 or i2s to hdmi input pin numbers for the audio gd.
audio-gd.com/Pro/dac/I2SdefinitionEN.htm
and here the i2s connectors.