I have been engaged in technical work in SMT workshop for 5 years. To answer your questions above:
1. All SMT machine operators are standing up. There's no place to do it.
2. You can walk around when you work, because the operator has a wide range of work, such as: taking materials, feeding materials, sending the first piece for inspection, bulk material processing and so on.
3. The labor intensity is general, and the operator has higher requirements, more skills and stronger understanding than the printer, middle inspection and eye inspection.
Operator is the best job in SMT workshop, I hope you can do it well. (Most of the factory operators do not recruit outside, but from the internal work of the better people promoted)