Puff of smoke is normal when starting from cold, but this should clear up fairly quickly. Check for excessive breathing as this can indicate wear or cracked pistons. Oil vapours can get drawn into the intake by a heavy breathing engine. This can be 'fixed' by moving the breather hose into a catch bottle or down the chassis rail, but that just hides the problem.
On the road, it should cruise happily at around 60-65, without being too smokey. If you've driven a NA it should feel a little more powerful than that, but not quite as much go as a TDi.
They're good engines for their time, but they need regular attention. If it's been well looked after and is still running today without any obvious symptoms, it's unlikely there's anything seriously wrong with it.