Re: "not giving Windows 10 enough headroom"
Windows built in partitioning tool is almost completely useless. Fine for shrinking to create additional new partitions or removing whole partitions, but that's all. It will shrink the partition on only one side ( right I think) to create a new partition there.
If you try to redistribute space it will only shrink on the one side or allow the adjacent partition to grow on the equivalent ( i.e. far) side where there is no space.
So, in the screen shot I can't grow the left partition, having shrunk the right one ( should I need to)
https://www.dropbox.com/s/yb1oumek4hpgmyy/hdd%20spaces.jpg?dl=0
Of course I use 3rd party s/w instead.
Biting the hand that feeds IT
