Hey there! Signed up for the forum just for your post lol.
To answer your question: No, it does not make it too twitchy. I have the DDMWorks rear torsion bar and the Whiteline fiesta 22mm rear sway bar (BFR80) installed and it made the rear end nice and crisp.. PROVIDED you also upgrade the front rear sway bar too.
When I had just the rear upgraded with both of these bars, I noticed the handling dynamics changed towards oversteer quickly. Of course, it was a lot of fun since the car comes with severe factory understeer syndrome! But I wasn't completely satisfied without having played around with the front.
I decided to upgrade the front sway bar too but was wary of going too thick to avoid inducing understeer. I went to my local junkyard where there was a 2012 Fiesta, dropped the subframe, and removed the OEM 22mm front sway bar and corresponding brackets. This is a drop-in fit for the Mazda 2 DE.
After slightly lowering my M2 DE's subframe I was able to remove the OEM 18mm front sway bar a lot easier. I also went with Powerflex 22mm polyurethane bushings (street/purple) and I'm quite happy with them. The end result: the car's handling is now fully neutral, with just the tiniest touch of oversteer which I'm very happy with.
Hope this helps!