Honestly it is hard to say. I have no experience with the game you are playing. The fact it is BETA would make me think that likely it has issues with its engine optimization, so a game issue. If other games are fine, I would really think this.
The other thing is that usually adding an overclock to the APU can be problematic. In fact any OC can be on any processor. Some think that just because it doesn't blue screen or lock up that the OC is beneficial. Many overclocks cause processors to throttle when they otherwise would not. Many OC's look good in benchmarks but throttle like crazy in games. So it is really hard to say. I would remove any over clocks and see what you get. Then test other games to see if they exhibit the same behavior.
Again I do think that it is likely just this game. I did a quick google search of valorant beta frame issues and got a lot of hits. People with much more powerful hardware than you on team red and green saying they only get 20-50 fps at low settings.
Being a beta the game engine and likely the drivers just are not optimized.
Even the fact that it tanks when you join an online game screams game issue. The AMD driver doesn't care you are online. The game engine and its netcode and how it handles multiple users does.
I would give your feed back to the the game developers support department. Usually this is what they are looking for during a beta.