Ahh, well its not the way I look at my own system, I've never had a reason to consider any of my inputs and outputs. The OCD is not strong in this one.

For me:
Variety is key.
Spare space is good to have, I will never ask "what should I put in my remaining 4hp" ;-)
I tend to cluster modules of things I want to use together.

Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.

https://youtube.com/@wishbonebrewery