The Ryzen 5700G 3.8 GHz octo-core cpu The Blackrock Pro 4 has 2 fans and the case has a fans directly behind the cooler. I want to know if it's worth it to get a new case and the liquid cooler.
For a 5700G, no. That CPU should operate just fine within its stock limits even with the Wraith it comes with. IMO even the Dark Rock is complete overkill, and AIO even that much more so.