Will upgrading to 16GB of RAM fix my stuttering and lag with 30+ tabs and streaming video?

Yes. 8GB systems choke when Chrome eats 4–6GB for 30 tabs plus streaming, and the OS uses 2–3GB — once memory runs out, swapping to disk causes stutter. Going to 16GB gives Chrome room to breathe, keeps tabs in memory, and eliminates the lag. If your laptop can be upgraded, do it — it’s the single best performance fix for this situation.