Landscape Material

Ok someone help me understand, i came from unity and landscape painting was as easy as adding the textures/bump maps and off you go. tho UE4 landscape tools seem more robust by far, im finding it a bit difficult understanding…so

what if i purchased a material pack from the market place i can just drag that as the landscape material in the detail panel right? but what if i want to add to that landscape with that material on?

ive seen most tutorial showing how to do this with various textures to create your own layer blends, but if this is the way to go should texture packs hold more interest than materials (well in landscape cases i guess)

i understand you can use the premade materials for the landscape and that may be ok for most, but my thing is further modifying/painting on top of said material, will i then have to recreate the material with the current textures plus the new ones i want add anyway?

thanks in advance for any clarification guys