The Longitude doesn’t have boost spacing so even though it’s a plus bike it won’t take massive tyres. Makes it more compatible with “older” tech so better for sourcing cheap parts, QR wheels, dynamo hubs, etc…
There was a thread the other day where someone has put 3.25″ on the front and 3″ on the back without any issues. If you want to go bigger on the back you’ll need to run a 1x setup so the chain doesn’t hit the tyre in the lowest gears. I don’t think Superstar offer any plus rims, so the Alpkit rumpus would probably be the best value, especially as they offer a dynamo build I think?