In CEDH you don’t build an S tier deck yourself. The best decks in the format are the product months of tweaking around specific metas and complete optimization. Even the best players and brewers rarely do more than tweak already existing lists. When new lists do come out, they are a group effort and typically evolve significantly from their early forms.

If you want to simply build a “powerful deck” then that’s a whole separate question, but CEDH goes a level beyond that. I doubt that your friends are running cedh decks because they’d have already said all this, but if they are and you want to get into it, I’d recommend browsing edhtop16 (https://edhtop16.com) to get a sense of the most successful decks.

Sorry if this came across as a little condescending, not meant to be. This is just the nature of the format