In the Jewish faith, the surname Cohen (and it's various spelling) denotes that historical, ones ancestors were priests in the Temple of Jerusalem. It's a really important name, and I know using it as a first name really rubs several of my Jewish friends the wrong way. They feel it's disrespectful. I would encourage you to take it off your list.
I voted Cohen. I know 2 and think it's a really strong calm sounding name. The only other one I like on your list is Oliver but to be honest I'm getting sick of hearing it. I think it's pretty much agreed it's amazing but sooooo popular right now which ends up seeming boring to me.l
James and Everett are my favourite options. I also like Jasper and Oliver. I prefer Liam as a nn for William. Don't use Cohen for the reasons stated by pps.
Re: Which name do you like best for a boy?