I don’t plant to repel from an area. I do use lavender filled bandanna collars for our indoor kitties when they go out in the garden on supervised outings.
I have been maintaining a chemical-free yard and garden so I do believe there are microscopic and macroscopic natural predators out there that control some of the flea and tick population — everything from nematodes to birds.
Also, more with some hopes of repelling mosquitoes, I grow patches of various kinds of mints including peppermint, spearmint, applemint (added chocolate mint and orange mint last year), monarda, lemon balm. They surround the patio and surrounding areas. I also have creeping charley growing everywhere, though not intentionally.
I don’t know about Catnip repelling ticks and fleas — what they do is attract cats — ours and stray ... they eat them and roll in them until the catnip is barely alive. I’ve moved my catnip patches to inside of 4 ft fenced garden beds and containers in raised inaccessible areas.
Fleas and ticks still make their way onto our indoor cats. Sometimes, they have encounters with mice, moles, voles, etc. during their outdoor forays. There are wild rabbits that “visit” the garden and sometimes even come up on the patio to help with the weeds growing between the bricks. I suspect that sometimes I’m the one bringing in eggs, larvae, and adults from them on my gardening boots. (our kitties sometimes sleep in my boot tray and sometimes just rub up against the boots for whatever reason).
Flea combing is a regular activity here. After trying to set various traps (only caught few to maybe a dozen at most), and scattering DE “flea powder” in the house (which tends to clog the vacuum cleaner), and thinking that best flea trap design would generate heat and self propel around the house to attract the pests, and then I would only have to periodically empty the trap.... It occurred to me that I DO have TWO OF THOSE — 4-legged, furry, warm, travel throughout the house, get into corners and under the couch sometimes, attracting and collecting fleas ... I just have to empty those traps twice a day during the worst infestation (by combing them thoroughly), and activate the bait-and-kill feature by DE-powdering the chin, neck, back, and leg-pits.