Open the Processes tab in Task Manager and sort by CPU utilization to see what application is causing the higher than expected usage.
Not sure what is meant by "fans not stable on idle", do you mean they are varying the fan speed due to the unknown utilization? If so that is normal, fix the utilization and the fans should settle down.
As to only hitting 4.1GHz on Cinebench multi core test, that is normal as @misterj states. The 5700X is a 65W TDP processor that is restricted to only 76W PPT power limit, and as your screenshot shows it is hitting 100% of that during the test. If you want it to boost higher, increase the PPT limit.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT