NDI GPU decoding

I own 2 iMac Pros. I want to use one for creation and the other one only to stream to Restream with Wirecast.

I use the NDI to bring my creation to the computer with Wirecast and works great, but I do not know what is the  GPU Decoding supposed to do? would it be better to activate it?

My streaming/wirecast machine specs are:

iOS Catalina

3,2 GHz 8-Core Intel Xeon W

Radeon Pro Vega 56 8 GB

32 GB 2666 MHz DDR4

What would be, with that setup, the highest quality output you'd chose for Youtube at 1080p30:

x.264 H.264 or Apple H.264?

Thanks a lot