No - theyre not the same. All Mk1 Clios bar the 16v/Willy/RSi have Bendix callipers and discs. The others have Lucas callipers and discs.
Yes - theyre better and theyre simple to swap. Ask BenR - he did it to his old RT.
Its possible to stick a Valver engine and box in your RT, but its very expensive versus just buying a Valver and then theres the point that the 16v isnt just an RT with a bit of lowering and some wheels - it also has wider tracks, arches to take the tracks, a four-bar torsion beam system at the rear (as opposed to two on the RT) and loads and loads of other stuff it would take you ages to replicate. Fine if you love your RT and have a wadge of cash - but not otherwise! The GT Turbo conversion is popular.