Just FYI, I ended up digging up all the weeds and pulling out all the wood that the previous owner had inserted into the gaps (was a huge pain in the ass to do this!!!) I was unable to pull out all the wood unfortunately, but ended up filling all the gaps and covering it up with Envirostone. Looks good, time will tell to see how effective it is in preventing weed growth
EnviroStone from Envirobond