If 90L does become a Tropical Cyclone, the only noticeably different impact could just be a greater chance of a more consolidated, maximized area of heaviest rainfall ~ but not necessarily the highest totals, as these can be achieved without core rains given the likelihood of ongoing training bands of rain/thunderstorms and the squeezing out of moisture as this system interacts with the impinging front to its north.

Given how saturated both the ground and air is or is becoming in the southern states, combined with strong upper-level exhaust, it may maintain as a Tropical Cyclone for quite a lot longer than expected. Alternatively, it could also encounter too much shear and shred apart. But one thing is certain: flooding.