Hi Katelowri,
Others will have all sorts of good ideas - but don't dismiss couch grass paths out of hand. It's what I have. Yes, the beds do need edging - once or twice a year; the plants seem to learn it just ain't worth trying to grow into the beds, and I get fewer "adventurers" each year! And I occasionally cut them.
But, the more I leave my paths like this, the more I suspect they are my best defence against slugs - partly because the slugs retreat under the grass overhanging the bed edge; easy to find, and easy to squash! And the slugs lay their eggs there too - trim the edges a week or so after rain, and I see several clusters ------ out into the sun to bake, or for the birds to find!!!
All best - Gavin