Windows 10 likes an empty drive to install on to - no partitions or anything. From a purely personal point of view, If I'm installing Windows I use the setup program to delete everything on the SSD and start from scratch (bear in mind though that my Users folder and one or two other things reside on a physically separate device so I don't have to account for them in the initial setup).
And there's significant anecdotal evidence that having an SSD at over 50% capacity has a very detrimental effect on the speed of the device.
Oh, FWIW, my SSD is a SanDisk 240GB - It's not missed a beat.