Volatility matters. Crypto needs a higher RSI period (21) to filter noise. Forex pairs like EUR/USD work well with 14. A proper book includes a volatility-adjustment table.
What is RSI? - Relative Strength Index - Fidelity Investments rsi pdf book
: Exploring advanced methods like the RSI 80-20 strategy or combining it with other technical indicators. 3. Rhetoric of Social Intervention (RSI) Volatility matters