madmatt30 :
Nvidia to nvidia - no need to uninstall, I would just run the latest driver package again though , sometimes not necessary but for the sake of 3-4 minutes good practice.
This is the correct answer. You probably don't need to uninstall, but you definitely should reinstall. Personally I would uninstall and reinstall just to be safe.
Although the drivers are universal, each video card has different hardware. The install process will tune various settings to optimize the driver's performance for your particular hardware. e.g. If a 1070 does a certain tesselation computation faster than the 980, the driver will be tuned to prefer the faster process on the 1070. If you leave the drivers as-is from the 980, your 1070 would end up using the function which was faster on the 980 but is slower on the 1070.
Older video cards might not even have hardware support for functions present in newer cards. In this case, universal drivers are configured to perform the function in software. If you retain the original drivers in this case, this hardware that is present in your newer card might not even be used because the drivers would automatically run the function in software.
(In theory, the drivers ideally should auto-detect your hardware and reconfigure themselves every time you use them. But in practice as a programmer, I've seen way too much stuff hard-coded to just "trust" that the programmer did things the right way, instead of the easy way.)