Hi and welcome! Its a great idea to start preparing ahead and this is a good place to start. I‘ve learned loads on here during the five years I‘ve had my dog, its all good advice based on experience.
Humphrey is show line and is very laid back anyway so I‘ll leave the advice to the COL‘ers with working cockers, the only thing I would say is that mental stimulation, nose work etc requires a good deal of energy, so if the dog is given the opportunity to use its brain, its not always necessary to offer huge amounts of physical exercise every day. The balance you‘ve described sounds fine to me.
Although balls are a great way to exercise, its easy to fall into the trap of just becoming the thrower to a ball junkie and gun dogs love nothing more than the chase, so rather than just chucking it for the dog to fetch, you can integrate into training other things, ( and training in itself is all „work“ for the dog and will use up energy). It might be an idea to have a look at some of the training videos, youtube etc for advice or consider contacting a gun dog training class.
Keep us posted, looking forward to news of the arrival!!