It depends... Do you have a secondary hard drive installed. If so, then YES you could easily do it. I've never used more than 60GB on my SSD.. and it's fully loaded.
There are tricks you can try.
For example...
I've done the dual booting thingy many times in the past and what I do is.. I RELOCATED key folders from the O/S of the C Drive: Documents, Music, Videos, Pictures, Saved Games & Downloads... to another drive. NEXT... I installed a second O/S and relocated those SAME EXACT folders to the same location as the other O/S so they use the same folders. That cuts down on space used (no duplicates) and if I booted into the other O/S, any changes I made from the the other O/S stays constant...
The only problem with that approach, if you were to use a smaller SSD, would be the Windows 10 Apps. From what I can tell, there currently isn't a way to select the download location for the Windows Store.. so everything will download and install to the SSD..
So, YES you can use a smaller SSD without any problems... but if you plan on using the Windows Store to download apps then you should consider a larger SSD.