"roadholding as well as wind resistance"
........usually has nothing to do with struts or shocks. Those struts usually last a very long time, actually most 850, X70 owners NEVER replace them as they don't just "go bad" like the old Goodyear and Firestone adds would like you to believe.
Unless they're noisy, binding, causing the car to bounce excessively, leaking oil.....there's no good reason to replace them.

Tires are more likely the reason why your roadhandling might seem to have decreased.

Many who buy Bilsteins later report that the ride is too rough and that they then feel every crack in the road so I wouldn't rush into those.