Disclaimer : at the moment you open the partitioner on the installer GUI you are on you own and will have to create raid, and whatever you want, the default SME partitioning will be replaced by either CentOS default or what you designed. Only way to go back is to reboot.
That being said the partitionner is quite flexible and allow you do do almost all what you want. You could chose to do
/boot 1GB xfs
/ 50GB xfs
/home/e-smith/files 200GB ext4
/var/affa 500GB ext4
Just take the time to put the important pieces first and then set one to take the remaining space.