I think the most important thing is learning how to ‘fight fair’. How to have discussions and arguments calmly, or reasonably calmly, expressing your feelings and your reasons without any personal attacks. Also accepting a bit of win some, lose some, or compromise depending on how important the issue is to you.
My partner and I have had some big disagreements over the course of our relationship - e.g. marriage vs no marriage! As well as ideas about living more sustainably etc. And parenting has brought up lots of things such as him wanting to try timed patting and shushing leaving baby to cry in a crib vs me not wanting to sleep train or leave baby to cry at all, discussion about to home school or not, arguments about the division of labour around the house…
It helps that even if we have different views about how things should be done, we have the same core values and same ideas about the type of child we want to raise. We have similar political views, we both value gender equality, we both value each other and our friendship, we both want to raise children who are kind, secure, happy, independent, intelligent, critical thinkers. Those things are more important to us than a child being ‘obedient’, or playing a particular sport, etc. I think if our values and ideals were very different it would make parenting together really hard, but when you’ve got the same core ideals then it just comes down to careful discussion about the best way to get there, where our limits are, stuff like that.
E.g. with spanking it might be helpful to discuss what you’re hoping for when raising your children. Is it more important that they do what they’re told straight away as children, or that they can make responsible choices even without someone watching or telling them what to do? What message might spanking send - that it’s okay to hit/hurt people smaller or weaker than you to get them to do what you want? Are there other, more positive ways you could get children to behave? But yeh, like you said, you’re young and kids are a way off anyway, so I guess a lot could change.