In my humble opinion, there are a lot of issues that are treated within liberty of conscience in the PCA, which should be so treated, that would have binding rules one way or the other in, say, the OPC.
This is anecdotal, but one time in nominating men for office in my former OPC church, I was told by the then-pastor that he would not support candidates who smoked or were in his opinion too fat.
I'm sorry, but I couldn't find anything on things like that in the Biblical criteria for office.
Being temperate or self-controlled might be evidenced or proven as lacking by these traits.