Soldered RAM is not slower.

Latency is essentially the same. The RAM chips inside soldered and socketed modules are the same parts. Soldering doesn’t add meaningful signal delay—the trace length on the motherboard is negligible compared to the nanoseconds we’re talking about.

The real difference is upgradability and repairability. Soldered RAM is permanent. If it fails, you’re replacing the whole board. If you want more later, you’re out of luck. But performance? No penalty.

Don’t avoid soldered RAM for latency reasons. Avoid it because you want the option to upgrade later.