I've seen this ship pop up a few times, and honestly, the tension is kind of built-in from their canon dynamic. Gigi always felt like the character with the plan, the one holding everything together but maybe hiding the most underneath. Finn’s more reactive, following his instincts. So when you pair them, you get this push-pull between control and chaos. A lot of writers play with Gigi trying to keep Finn at arm's length to maintain her own stability, while he's the only one who can see through her walls because he doesn't bother with social niceties. That creates a constant low-grade friction.
It's not always explosive tension, though. Sometimes it's quieter, more about unsaid things. Like, maybe Finn makes an observation that's a little too accurate, and Gigi has to deflect, and the whole scene just hums with what they're both not addressing. I read one story where they were stuck in a supply closet during a storm, and the tension came from Gigi meticulously cataloging their remaining rations while Finn just sat there, asking her why she was so scared of running out of time. It wasn't about romance at all in that moment, just this raw, character-driven friction that was way more compelling than any argument.
The 'sus' part adds another layer, obviously. It lets writers explore distrust or hidden motives, which can crank that tension from personal to potentially dangerous. Is Finn suspicious of Gigi's plans? Is Gigi wary of Finn's loyalty? That ambiguity becomes the engine for a lot of plots.