Is it possible to have two Fronius Smart Meters connected individually to two Fronius Datamanager Cards and have it as a single system in Fronius Solar.web?

No, this is not possible because having two smart meters under a single system will lead to an incorrect visualization of the consumption values in Fronius Solar.web. However this is possible when one smart meter is set to feed-in point and the other smart meter is set to consumption path. This configuration is possible only if a combination of Fronius Datamanager 2.0 box and Fronius Datamanager 2.0 card is used.