Can a 120mm AIO cooler handle a 9950X3D?

It sounds like you're reaching for overkill if you just want a small build. Unless you really need all those cores, a 9800X3D might save you some cooling headaches. Plus, if you're gaming on integrated graphics most of the time, maybe you don't need all that power anyway.

From my experience, a 120mm AIO will struggle. I’ve seen temps spike into the 80s with larger setups, and a 360mm AIO can barely keep up during heavy loads. You might be better off finding something that balances size and cooling efficiency rather than forcing a 9950X3D into a tiny case.

If a 120mm AIO is the biggest cooler you can fit, then you might not have many options. It could work, but without knowing what else you're doing with your setup, it's hard to say for sure. Just keep in mind that if you're limited on surface area for heat dissipation, your cooling performance will suffer, regardless of whether it's an AIO or a custom loop.

Honestly, a 120mm AIO isn't going to do the job for a 9950X3D. They typically offer performance similar to a single tower air cooler, which won't be enough for such a power-hungry CPU. It sounds like you're trying to fit a lot of heat into a small case, which might not end well. What case are you planning to use?

Building with a 9950X3D in a small form factor is definitely ambitious. It could throttle under load since that CPU hits 250W. If you're really constrained, you might want to consider downgrading to a 9800X3D instead. I haven't seen anyone push a 9950X3D with a 120mm AIO, and it doesn't sound like a great idea!