Almost every time when I've done it the "lazy way", I've then had some kind of issue and regretted it. So let me tell you how to do it right the first time and save yourself a lot of hassle and headaches. I know it is theoretically possible to have both installed, but the risk of conflicts and driver issues increases exponentially. Considering you don't need and won't be using (and in fact- can't use, since you'll remove the GPU) the old drivers, there is zero reason to keep them installed. Moreover, they will waste system resources for no reason. So, the best thing to do is to clean them out.
1. Download DDU (display driver uninstaller) - this is an app specifically made to thoroughly clean any trace of your old drivers.
2. Reboot your PC into safe mode. This does two things - first, it disables your internet connection, blocking windows from automatically downloading drivers. Second, it stops any other app from interfering with the driver uninstall process.
3. Launch DDU, select your GPU vendor and then "clean drivers and shut down". It will remove everything associated with your old drivers and then power down the computer.
4. Swap the old GPU for the new GPU
5. Go into windows as you normally would and download the latest drivers and Adrenalin software from AMD's website. Let it download and install everything it needs to and if it has to - let it restart the computer.
That's it. This will save you a lot of hassle with leftover driver remnants, conflicts, etc. In case you get issues with a specific game, that's usually due to that game having shader caches from the previous GPU. Either look up on how to clear this, or delete and reinstall the affected game(s).
Overall, there is nothing for you to fear. Good luck and enjoy your new GPU!