How can I reduce noise and fan revving in my new compact PC build?

I recently assembled a PC in a Lian Li A3 case with a 9800X3D, 9070 XT, and a 240 mm AIO. Because the RAM is about 2 mm too tall, I couldn't mount the radiator on top without it pressing against the memory, so the AIO is currently mounted on the side as an intake. I also couldn't install all three planned bottom intake fans: the motherboard's front USB 3.0 connector blocks the middle position, and the GPU support bracket blocks the front position. The current layout is one bottom-rear intake, one rear exhaust, two top exhaust fans, and the side-mounted AIO intake.

The system is louder than expected, with a persistent hum and noticeable fan revving. Before adjusting the curves, the CPU repeatedly jumped between roughly 42°C and 60°C at idle, although a Windows update may have been running. After changing the ramp-up and ramp-down settings, idle temperatures are steadier at about 39°C. Startup briefly reaches around 65°C, and YouTube playback keeps it near 39°C. I haven't tested gaming yet. What fan curves or airflow changes would help reduce the noise and humming without causing temperature problems?