I find they overlap somewhat. Yes, they are two completely different concepts, but the end result is that without both, you don't have access to certain parts of your phone, like /system. You need both to have write access to /system, which is where the OS resides, along with crapware, boot animation, superuser, etc.
So if you want to remove crapware, having root won't be enough. That's why when we talk about rooting an Android phone, the word encompasses unlocking the bootloader as well. You may also hear "half root" vs "full root," where full root includes the bootloader unlock.
Some half-root exploits temporarily unlocks the bootloader (or more appropriately, disables NAND protection), so during the exploit, things can be written to system. Might not be possible on E3D due to the individually signed partitions.
Anyhow, the two concepts are plenty intertwined when it comes to getting more freedom out of your phone.