Is it advisable to sous vide in steam fresh bags, the type where one cooks the veggies in the microwave for 4 minutes?
No, in addition to the valid reasons offered by @GdD sous vide relies on conduction to transfer heat from the water into the food being cooked. "Steam Fresh" bags are not vacuum sealed. The air in the bag is an insulator between the water and the food, making the heat transfer more difficult and uneven.
While vacuum sealed bags are preferable for sous vide a 'near' vacuum sealed, such as air being forced out of a ziplock bag, is functionally 'good enough'. The volume of air in a steam fresh bag would be problematic.