CW's demeanor, method of killing, lack of screaming heard by neighbors and the way he hid the bodies all point to this being planned by him rather than being about rage. If SW had planned to confront him about his cheating that night, she probably would have mentioned it to her best friend Nichole beforehand, so it's very unlikely they argued about that.
Given that everything points to him planning the murders, it is surprising how inept has was. He obviously didn't anticipate being unable to put SW into an oil tank and her friend stopping by so soon and calling LE.
CW is a mechanic, so perhaps he did think about his phone being tracked along with his truck if it had a GPS. He could have left his phone and detached the truck GPS and temporarily left them at another worksite. From the affidavit we know that the worksite where their bodies were recovered was first identified via a drone which showed a bed sheet. Drones may have been used at many of his worksites. He only confessed after they identified the particular one where he left them.
It's still confusing to think about what his plan was for SW's phone and car. He knew her phone could be tracked and a leased Lexus would almost certainly have had tracking on it.
He had to have know that he would be THE suspect in the disappearance of his family but must have thought they couldn't charge him without physical evidence. So it's doubtful that CW was all that concerned about being outed as a gay or bisexual if he wasn't worried about being suspected by almost everyone for murdering his family even if his plan had worked.