Download and install the new Adrenalin 2020 Control center 
Link below

https://www.amd.com/en/support/kb/release-notes/rn-rad-win-19-12-3

Most of the problems I have encountered answering questions similar to yours are that users do not have the GPU set up correctly in the Control Center and are gaming on their Dedicated Vega 8 GPU which gives poor performance and is not designed for gaming. I have your exact model and my gaming experience using the AMD 2020 Control Center is good, Follow these instructions

First make sure you game with your battery charged to 100% BEFORE gaming and KEEP plugged into the main AC power while gaming. Make sure "High Performance when on AC", is selected in your Windows Power Plan and in Nitrosense. If you fail to do this your CPU will run at around 50% of capacity and you will experience poor game performance

Open the New AMD 2020 Control Center and click the GAMING tab then click the 3 dots in the upper right hand corner and select ADD A GAME, navigate to your games .exe file and double click it to add it, or you can select SCAN FOR GAMES and let the Control Center search your harddrive for games to add. After successfully adding the game click on the game and you will be taken to another window and click the LAUNCH GAME tab.
Only in this way will your games use the Discrete Rx560x GPU, NEVER launch your game through a desktop shortcut or any other way, do it in the manner I have described.

Please remember that online gaming may experience low fps and stutter due to the games servers and bottlenecking and that has nothing to do with your GPU.