While multi-GPU configurations usually do not scale well and are not that popular these days, it is good to know that you can pair two RTX 2070 Super cards in multi-GPU setup, but do not expect any miracles as scaling heavily depends on the game.
While we haven't seen many reviews with NVLink included, Anthony Garreffa from Tweaktown.com did a neat review with a couple of games at 1080p, 1440p, and 2160p resolutions. The biggest gain can be seen at 4K resolution and in Shadow of the Tomb Raider game, with an impressive 86 percent boost over a single RTX 2070 Super.
Of course, the performance boost can't justify the price of another RTX 2070 Super, but with further driver tweaking, it is possible that Nvidia will raise the performance a bit higher, but nevertheless, going for a higher-end RTX 2080 Ti or investing that money in the rest of the hardware is a better option.
In any case, you can pair two RTX 2070 Super cards in NVLink multi-GPU configuration.