Check-in Luggage is included from US to Riga (Latvia) for both tickets. Meals are included.
This flight arrives to Stockholm in the morning, on 07:15, on September 4. Flight duration: 7h 55 min.
So, you can fly to Stockholm, and not fly to Riga at all if you don't have checked-in bags.
If you continue to Riga, the layover in Stockholm is 8 hours, and flight to Riga departs at 15:25, with arrival time on 17:30. Flight duration 1h 05 min.