KONI Sport dampers (yellow) are adjustable for 'rebound' (as opposed to the 'stroke' as well). the adjustment is via a little tab at the TOP of the dampers, using the supplied plastic knob/key. at the 'softest' setting, they will be like the original dampers, though better control. they have about 2.5 'full turns' of adjustment, but you may only use up to around half a turn to attain the comfort/performance you want. basically, adjust them until the car no long 'bounces' over a series of undulations. they come into their own at higher speeds, and not really for tiny ridges/bumps; more the highway undulations.
i recommend starting with say a quarter turn, and work from there, and maybe only readjust after a week or so or when you can easily detect it's too much or too little. then do another quarter turn; shouldn't be necessary to do much more than that at a time.
i've not changed ARBs before. they will certainly impact on comfort though if they are significantly thicker (2mm thicker is enough for a noticable effect; other factors like the actual metal and length of the 'arms' also affect overall stiffness). if you don't like them, just change them back. i think the standard ones are ok (i kept them standard when i had a 156, but used KONI dampers and Eibach springs).

GT . 3.2L V6 . Q2 . Kyalami Black - Red . Eibach . KONI . ATP 19" . TOYO Proxes4 . Mille Miglia exhaust
155 . 2.0L 8V TS . Grigio Grey - Grey . Eibach . Bilstein . Enkei 17" . Bridgestone RE001 . REMUS