Qatar Airways seat assignment and student baggage benefits

My partner and I are flying economy with Qatar Airways on the route CPH–Doha–Bangkok and back. If we don’t select seats in advance, will the system usually assign us seats next to each other automatically?

Also, the tickets were purchased through my boyfriend’s account, which has the student Privilege Club benefits applied. If I add the booking to my own Qatar Airways profile, would I also be eligible for the extra 10 kg baggage allowance, or does it only apply to the account holder?

Thanks in advance for any insights.