other than using dupont connectors to attach wires to the gpio header for fan and button enhancements you can solder the wires to the underside of the pi board gpio header. easier than you may think soldering is 90% practice and 10% confidence..
the single wire dupont socket connectors are less secure than their multi pin counterparts but can be secured with a slither of clear tape, a drop of hot glue or if you have the budget electronics solastic.. the 40x headers are 40x stiffer as they have 40x the grip
Dont let the button feature steer you. A simple button addition to most cases can be achieved with the nice and cheap single sticky backed membrane buttons..
as long as the case has a flat surface to stick the button to you should be good to go.
https://www.aliexpress.com/item/3262908 ... web201603_
link is an example only..
Yes more dupont connectors .. but they do work and are ok
just add tape
My only concern with the case/fan linked to is the 30mm fan size 40mm is WAY more common and a noisy fan is VERY annoying. sourcing a quiet 30mm fan may be harder than finding a quiet 40mm fan
also check out the fan shim which you can use in some non fan fitted cases..
another 30mm option the irony didnt escape me..