At 4 months definitely a male. As you mentioned some pullets can have respectable combs and wattles but those are pretty big. Cockerels combs and wattles typically turn red early while a pullet's do not until she is ready to lay. I have had some pullets lay that early but again the color is a big hint. Heavy thick legs are a good sign it is probably a cockerel but is still a very good hint. Not all thin legs are pullets. Look at his posture, very upright. Pullets are generally more horizontal to the ground. But the tail feathers are starting to curve down. All the other stuff are clues, some pretty strong. But those tail feathers curving leave absolutely no doubt.
With all the hints you can often tell the sex of a chick around five weeks, especially with a little experience. But I've had some I wasn't sure until his age. To me it is usually easier to say that is definitely a male than it is definitely a female. Most males start to show these signs earlier than females, but not all. Some males can be really slow to develop.