Can I mix a 16GB and a 32GB RAM stick for 48GB total?

Yes, but with caveats. Most modern systems run in “flex mode”: the first 16GB from each stick runs dual channel, the remaining 16GB from the 32GB stick runs single channel, causing a small performance hit in memory-sensitive tasks like gaming or video editing. Stability is the bigger issue—mixing brands, speeds, or timings can cause crashes, so only do it if both sticks are the same brand/speed/timings. If buying new, get a matching pair instead.