Would I notice a difference?

[ekvtec]

But I mean specifically whats the difference? I'm not 100% but is it that coilovers will absorb more thus less 'bouncing' or ..? Also is there a resource with mods explained that would be fit for auto cars? Thanks

Depends on your budget really? If you just want lows with close to stock feel go springs, but if you want something more stiff and less body roll,better driving feel, etc etc go coilovers

I recommend going coilovers if you get the 17x9 wheels, because the car will bounce alot with springs and might hit/scrub the wheel/tyre quite a bit unless you set up tonnes of camber

So I should be looking at different specs for Rota DPT 17 x 9 +35 all around wrapped in Kumho KU31 tyres, guards rolled and king springs?

Nothing wrong in this wheels specs, from past experience I would recommend 17x9 as it does sit flush with the guards, however you will have to roll your rear guards

Hope this helps