Does n vidia graphics gt 820 comes with a default optimus technology?

Hi, i had a old samsung laptop with nvidia optimus technology but now i need to change my laptop. Now there's no samsung laptop available so i found other new laptops in dell and lenovo,
its put nvidia gt820, the shop person also tell that that is the latest and its 2gb graphics, no 1gb graphics is coming now. The specs are i5 4th ge, 4gb ram, 1tb hdd, nvidia 2gb, so and so ///
the shop people says all the nvidia graphics are associated with the optimus tech in the latest laptops.
i have a doubt in that. Can anyone confirm that.
i models i have seen are,
1. Dell inspiron 3542 with dos os.
2. Lenovo G - series with the same config as i told above.