I think there is a lot to be said for having an overall idea in your mind about what you want to do in a given set. It also takes away much of the requirement to plan. You might select the the tracks you want to play but having something in mind will tell you how to get there.
At the micro level, you need to understand how to get from track A to track B and the skills that are required to do that but the overarching thing to aim for is what you want to do with the entire mix, or at least what kind of sound/vibe/direction/theme you want to take the mix in because that will ultimately inform how you put the tracks together.
When I first started playing in clubs/bars/parties, you would frequently come across DJs who would be completely focused on beatmatching. That is important, of course, but it can blind you to how you structure what you are playing and to develop subtleties that a better DJ needs. You could play alongside someone that plays at one level and was unwilling to vary it or have any regard to what the people before or after them would play. It would become fairly obvious they didn’t care about structure and the approach was “bang bang listen to this, bang bang listen to this”.
You can learn a lot by playing different styles/genres within a mix because it teaches you to look for the elements that link tracks together. It can sound really bad when you get it wrong but when you get it right, you will begin to note what made something work. It is much easier to play within a certain genre and will sound better on a more consistent basis but it can also limit your progress if you are not able to move outside of your comfort zone.
Another way to develop is to play old house records that don’t have a steady tempo and aren’t as polished with respect to the way they are produced because you really have to look for the patterns that link the tunes together and you can get punished badly if the key/vocals./percussion/energy of the track clash. Playing digitally, being able to warp tracks and sync take the majority of that away but having that other dimension helps to prevent you from getting lazy or falling into a siloed way of playing.
Someone else mentioned about playing across a range of BPMs, which is also a good tool for getting from slower tracks to more energetic tracks and then maybe back again because each tier of what you play will have its own style that requires you to link to the next tier.
