you’re already making more assumptions than you should be. Context is key. If you’re doing multiple assistance exercises, it is not safe to assume that, say, chins are always better than something like rows and curls.
Same issue applies to your next 2 questions. Incline db presses are significantly different from close-grip benching. Neither is simply ‘better’ than the other. Both are useful. And same goes for good mornings vs RDL’s. All these depend on where YOUR INDIVIDUAL WEAKNESSES lie. And that’s a case by case thing.
So all the being said, every movement you’ve listed is a good one. If you’re choosing from good exercises, it’s not going to be a terrible thing to avoid variety. You can still improve. But I’m of the opinion that regular variation is a better choice than what your approach will be. You’re majoring in the minors though. Unless you’re lifting at an extraordinarily high level, like well above the elite marker in powerlifting, you won’t actually see a real difference between these approaches that you can attribute to the assistance movements themselves. And because of other life factors, you may actually end up being misled to think one 12 week cycle was better assistance-wise than another, simply because you made more progress based on factors you’re not considering. Maybe you got better sleep that cycle. Maybe you ate better. Etc.
Anyway. Best of luck. Overall message here is: don’t sweat the small stuff. Just lift regularly and with intensity and you’ll be just fine.