I did not feel any difference between the two economy sections of SAS in terms of pitch. There is good pitch only in the bulkhead area and right behind the Plus section.
The drawback of the last rows is that they receive service last and the rows might be misaligned as the plane gets smaller towards the tail of the aircraft, otherwise no difference.
Regarding miles on Plusgrade it states that it only counts for Eurobonus (no other programs), but it was stated earlier in this forum that people could credit it nevertheless to A3 or other programs. But this is only courtesy and might change any time without notice.
Planes can switch depending on breakdowns and maintenance work that requires rescheduling. A330 are though more common to EWR and ORD as they are one of the shorter long-distance routes, while A340 are predominantly on long-distance Asian routes and the SFO route from Copenhagen.