As Prof. Le Duigou said, when hybrid biocomposites are mentioned, it is generally plant fibers and glass fibers together to make up for the lower stiffness and strength of plant fibers in comparison to synthetics fibers.
If you want to use different types of plant fibers together, you may select fibers from different classes, such as bast fibers (jute, flax, hemp, ...), leaf fibers (abaca, sisal, ..), seed/fruit fibers (coir, ...) to see the effect of fiber classes on composite properties.
However it should be noted that plant fiber properties are highly variable and they are affected by numerous factors which can be confounding.
The composite properties that can be tested are tensile, flexural, impact properties, water absorption, thermal durability, fractured surface imaging...