CAS panels are set up from a pool of KCs CAS nominate the chair and each party nominate from the pool, so not a UEFA paid member as such
The PL commission is different PL have a retained KC, a lot has been made that he is an Arsenal fan and it's been said that City have objected to his involvement. He is asked to set up a panel of three, he may or may not sit, on the Everton panel were two KCs and a sports financial expert. The hearing you refer to will only properly extend to the panel and City's legal team interviewing witnesses based on the submissions made by both parties. It will likely take a long time, unlike a trial, the witnesses can be compelled to attend nor, will it open one day and continue day after day until it ends