MileagePlus and SAS

SFO-CPH on SAS is starting up soon and wanted to take advantage of it.

I have done some research but as I have never flown SAS and credited to MP and was wondering if any of you could help me figure out the following.

- I see that Economy Extra Y-B-S fares can upgrade into business with Star Alliance Awards. As this doubles the ticket price for what appears to be their version of E+, I am wondering if there is a way to see if those awards are available at booking, i.e. can I see upgradable space before I decide to buy the Economy Extra ticket?

- Any reason not to upgrade? I see lie-flat seats so assume they must be nice.

- I am a 1K/Star Gold. Anything special about that like special rows at booking like on Swiss?

- I can't see a seat map. Will I be allowed to choose a seat?

- I see Y-B-S fares credit as 150% PQM. Has anyone had any issues with this?

- How nice is the SAS A340? I usually only fly UA but did fly Swiss to ZRH last year. I imagine the experience is somewhere in between?

Thanks!