Long arms come in different sizes. HQ sweet sixteen, Baby Lock Tiara, etc. are sit down long arms. Some people call them mid arms. But as Leah Day says, if they don't have feed dogs, she considers them to be long arms. Some people with the large machines like Innova use a stool to sit and quilt.
I don't own any machines without feed dogs. So can't help much but thought I'd start your thread going.