I know you haven't asked, but you indicated this was your first go with Ubuntu. I wanted to share a few thoughts and take aways from when I first started.
Depending on the situation and ammount of drives you have, I'd suggest possibly using two different drives. When I started off the whole boot loader thing really made it hard for me to grasp (especially once GRUB 2 showed up). If you use two seperate drives to install each OS (note: have only one connected at a time while installing) you avoid that issue altogether. Most motherboards have F+10/11/12 option to select boot media. I use this method on some systems for various reasons to this day.
If you do install on one drive, I suggest you do Windows first. If you install Ubuntu on one partition then install Windwows, it can overwrite the boot loader and not care you have Ubuntu. Ubuntu, on the other hand, adds a boot menu entry for Windows if Windows is already there.
I will caution you that if you use Steam and Spotify on Ubuntu it places all of your files in your home directory first, so consider putting that on another drive. I have ~10GB free on my Ubuntu disk.
In the linux Steam application you can explicitly specify multiple installation locations, which can avert the need to mount /home somewhere else or play with symlinks. I've done it, and it works fine.
Oh, cool! Did they always have that?