Explain "I did a Sparky Mate live today". Did you just run the live system or did you do a full install? If the latter - after installation did you update and upgrade and full-upgrade and was it via the Sparky-aptus or via command line?
Have you done "aptitude show tweak" or "apt-cache policy tweak" ? tweak is just "apt install tweak" away. Quite similar to install gimp. And the other - "apt install dconf-editor" might be what you want.
The standard kernels are via Debian, search for vulnerabilities there.
if you are still on Mate on Ubuntu post "apt-cache policy dconfig" to see if there is such a program - what you probably want might be dconf-editor.
The Sparky Wiki and the Debian Wiki are home to many answers to questions.
If it is security that is foremost for you, all variants of Debian Testing are not for you. Security hierarchy is Stable, LTStable, Sid and last to receive security is Testing.