Slowdowns = lack of performance, your device is too weak to run this at full speed
Latency = delay between pressing a button and its result being displayed on screen
Runahead or preemptive frames = lesser latency at the cost of higher requirements, meaning more slowdowns if your device was already too weak without those features
Runahead and preemptive frames aren't features to remove slowdowns.
Note that some slowdowns can be native to the games (because the real hardware was too weak to run them) and some emulators have the ability to get around this by overclocking the emulated hardware, yet again at the cost of higher requirements.
Your pi4 is simply too weak to run n64, and the only way around this is most likely to use a better device.