You get with OpenBSD on that one. Microsoft won't have anything to do with it.
Like any other Linux installation, BSD of all flavors will be similar. You will see the option of running it along with Windows during the installation. GRUB or GRUB2 will handle that on its own and takes over the control as the boot loader.
Secure Boot may be an issue. Most current version of Linux will install if Secure Boot is enabled but what it does is shut it off (for the Linux bootup). Not all of them do and you need to check on that before doing anything else.
OpenBSD should have the installation documentation on their site and you need to go through it and take notes before attempting to do it.
Personally, I do not recommend a dual boot scheme. There are times when GRUB gets an update and takes out the entire boot loader for both operating systems. In fact, the only way you can rescue the data if that happens is boot a "live CD" of Linux and copy the data off that way.
I do not recommend a dual boot scheme and would recommend a VM setup with either Hyper V (which is already in the machine) or VirtualBox from Oracle. That way, if something happens, Windows remains intact. BUT, that eats up storage space.
What you could do instead of doing any of the above is keep the tablet as it is and get the i3 model and wipe it out and put OpenBSD on it and have it as the Linux machine. If not the Pro 3, some of the older "Pro" models are still being sold and you can do it with them. That can be a bit expensive doing that.
By the way, Linux has no issue with the Intel Core i5 4200U "Haswell" CPU when it comes to video and OpenGL. That problem only happens with Windows 7 and Windows 8.