Hi Mindy, I'm sure so many parents share your confusion.. I think many of us go into parenting thinking, "well I'll just do what my parents did" (if they were good parents), but then we're bombarded with so much conflicting advice and opinions from all directions. At the risk of adding just another voice in the crowd, here's my 2 cents, seeing you asked..
First, don't conflate discipline with punishment - discipline literally means guiding and teaching. We do that from the moment our kids are born. If we can think of discipline primarily as guiding our kids to come to terms with reality (ie. Their self-centred reality vs actual reality), providing boundaries for them that reinforce reality and natural consequences, then we hopefully won't fall into the trap of punishing them from a place of emotion or how they've 'wronged' us. In other words, we're akways on their side, providing the boundaries they need until they come to internalise those boundaries - the point where we can let go. I've found the book 'Boundaries with kids' by Dr. Henry Cloud and John Townsend very practically helpful, especially when you're wondering what to do at what age.
Being on the same page as your partner is also really important!
None of us get it perfect but we can all learn from one another!

Nap deprived semi-working writer mom. Out to help parents embrace the struggle, find the joy and reclaim some sanity.