e30 rear disc brake vs drum brake and adjustable front strut

[markus_74]

I want to improve my old e30 and I want to change some part of my car.

rear brake
does rear disc brake will improve significantly over my old drum brake?

front strut bar.
which is better? adjustable strut bar vs fixed strut bar?
my old car has deformation so the range between right and left strut bar has change, can I use adjustable strut bar to fix it so it can be go to original range if I use adjustment on the strut bar?

thank you