|ID (11 bit)|Control Fields (7 bit)|Payload (64 bit)|… How can i assign 10 ids of CAN in 64 bits of payload
Priority is bit by bit in transmit order where dominant bits win, i.e. have higher priority. The priority is normally intended to happen on the frame ID. It's mightly late to detect a collission and worry about priority when reaching the payload bits.
It's 100% up to you to figure out how you want to make use of the 64 bits of the payload. There is an almost infinite number of ways you can select to allocate the bits.
You are the architect. So make up your design. But make sure you have a good reason for basically ignoring the existence of the frame ID - it's intended for priority and to allow hardware filtering of received frames.