Nothing living is going to work well. To most effectively keep weeds from encroaching and with the least amount of effort on your part, you need a physical barrier. Something like lawn edging or sheet metal strips about 6" wide. Just push them into the soil right against the fence or as close as you can get. Make sure they overlap sufficiently. They will be pretty much invisible and give you more room to plant.

Pachysandra grows very dense once it is established...which took about 3 years in my yard (photo below of grass separated from Pachysandra). I have only had to pull out an occasional weed, it's almost weed free and I really recommend it.

Or as gardengal48 (PNW Z8/9) says put in a physical deterrent. I bought some big rolls of plastic edging from HomeDepot brand "Vigaro"

to keep grass separate from borders and it's been a reliable solution and worth the effort of putting it in, instead of alway edging with a shovel.