Always a good idea to vary stuff even rep ranges, this article should be useful for you:
https://forums.steroid.com/workout-t...-training.html
From personal experience the training you do the first couple of weeks doesn't make the gains since the test hasn't kicked in. Once it kicks in you will hit PRs every single workout. For me its weeks 6-12 on enanthate or cypionate. Some people have it kick in week 4-5 I have even heard 3 weeks... But the gains come to a stop

What is useful to know about this is go balls to the walls during this period as this is the time between the point where serum test levels peak and saturation occurs. It won't grow any noticeable muscle without training, it is a response to training, so aim to get the greatest PRs be it weight or reps or both every workout.
You can do both rep ranges in a single workout btw. Start with a heavy compound exercise aim for the 6-8 rep range or whatever is heavy for you and then move on to other exercises where you vary the reps. But the heavy work should be first. The fast twitch muscle fibers are dependent on the load so you don't want to be exhausted.
Lean or dirty bulk didn't matter for me training is the same.