Yes, you can use both. This will not confuse your dog. You don't write if you use the word "yes" as release marker (termal marker) or as a duration marker.
If your "yes" tells the dog: "You have done it right and you'll get a reward", then he is released from doing this behavior, This is a "release-" or "terminal" marker, also called "movement marker", because we step back or away from the dog and insert a little reward event.
I myself use "ok". I also use sometimes the clicker, which has the advantage to produce consistently the same sound. If we use a word we must train ourselves to say it each time exactly the way (same length, same tone). Just a matter of practice
I prefer to use a word for three reasons: 1) As I give raw food my hand can be a bit slippery and then it is difficult to click exactly in time, which is so important. (Within half a second, the most!) 2) My voice I have always with me, I don't forget it and it already happend varios times that the clicker suddenly didn't work any more. 3) I often have my hands full of other things, e.g. the leash, a toy, a walking stick etc., then again it is difficult to click in time.
To use the clicker like your "Yes" as terminal marker is a good thing - but alternately, not at the same time -. Like this you always have a replacement. Important: You have first to charge the clicker, means you have to give the sound value, like you probably did it with your "yes".. This the dog will learn to understand within one or two days.
If you don't want to use it in the same way as "yes", not as a second terminal marker, you can use it as duration marker. E.g. You perhaps put your dog in a sit or down stay, you can click varios times to tell your dog to continue doing this exercise, to remain staying. I know reputable trainers who practice it like this. But of course the dog will only understand the meaning of that sound if you first train it with him like this in a easy manner.
I myself use as duration marker "good" ... "good" ....
It is not advisable to use it for different behaviors, This would confuse the dog. The clicker should always be used as a marker. For different behaviors you use first an averbal cue (command) like a clear hand movement and once he's got the behavior well you can start to introduce a verbal cue prior to the averbal one. Once he understands your command, you can fade the help of the hand movement or whatever you used and give only the verbal cue.
Hope that helps.
