Minecraft wiki entry for effect, associated text: In Bedrock Edition, if a target already has the status effect, a new status effect with the same amplifier overrides the old duration if it is longer, but a new status effect with a higher amplifier overrides any previous effect.
In Bedrock Edition, no matter whether the new effect can override the original effect, "hideParticles" value is always applied.
In Bedrock Edition, if the player uses an NBT editor to get negative levels of effects, the level of the effect jumps to 255 instead.