Oh, and getting rid of Cortana is like playing whack-a-mole.
A couple of weeks ago my perfectly working 9 year old Win7 laptop died (damaged power supply fried something). I needed a working PC urgently but didn't want to rush in, so I bought an old refurbished 2011 desktop on Amazon for £150 to keep me going. I'd avoided Win10 until now, but this has Win10 for refurbished PCs installed.
It's just taken me 2 weeks to get it almost back to how my Win7 box was running. Part of the process involved removing Cortana. I've got it down from 1.5GB RAM to 800MB on a 4GB sytem, I have Win10 using about half of a 50GB partition. It currently boots in roughly 20 - 25 seconds, down from about 50.
If you want to remove Cortana then this is how:
Spoof your browser to something other than Windows. You'll then be able to download the Windows 1803 .iso from the MS download site to your HDD. Download MSMG tools 8.7 from the link on MyDigitalLife:
You need an account to read the post on page 1 which provides the link to the latest version.
Back up your HDD, import the Windows .iso into MSMG and read the guide in the readme.txt for the version you've downloaded. You can then remove Defender, Cortana, Media Player, IE11, all store apps and a bunch of other bloat before you burn the .ISO to disc.
Bear in mind it can be a bit ruthless on the advanced Windows section. I found leaving the Store App and Edge browser intact keeps things running well. Even if you just remove Cortana, Defender and all apps except Store then it's a big improvement.