Will upgrading to 32GB of RAM void my warranty or cause overheating issues?

No and no. Most desktop and laptop manufacturers explicitly allow user RAM upgrades without voiding the warranty, as long as you don’t physically damage anything. Standard DDR4 or DDR5 RAM at stock speeds generates very little heat, so your case airflow handles it — no extra cooling needed. Just confirm the right generation (DDR4 vs DDR5) and form factor (DIMM for desktop, SODIMM for laptop).