Dual-boot Ubuntu / Windows 10 on SSD + HDD

Well, here's how I would do it:

1. Create and format all partitions to be used by Windows only.
2. Install Windows 10 in either BIOS or EFI mode.
3. Get a few cups of coffee while this installs.
4. Install Ubuntu from the CD/DVD, and select to use your own partitioning (Make sure to boot from the Ubuntu DVD using the same mode you installed Windows in - BIOS or EFI).
5. Create the Ubuntu partitions.
6. Let it install Ubuntu.
7. Get a cup of coffee while it installs.
8. Check to see that it boots to the GRUB2 boot manager.
9. Boot into each OS and make sure both have Identical network configurations. e.g. IP address, hostname, etc. You might want to add an identifier to the end of the hostname to distinguish which OS you're in, like this: MyAwesomePC-Win10 and MyAwesomePC-Linux.

This is my solution. I think you shouldn't divide your SSD drive to a lot of partitions like that. It will make your SSD slower. I think you have to choose 1 OS to install all of that OS to SSD drive. Because you just have 256GB SSD so I think Linux OS is a good choose. SSD:

/          20GB
/usr       80->100GB
/another....(don't need /boot partition as little partitions as possible)

At this time, Linux supported a lot of program. If you are woking in computer science, I thought you had to install a lot of very heavy program like: Visual, CSS, Quartus,.v..v. So 80->100GB is enough for install all of that program, and maybe you play game too. Your HHD you will install all of Windows OS, and store films, documents,..v..v That is just my opinion. Good luck bro