First I think it’s important to note that four swords and four swords adventures are 2 separate games.
If you want to play four swords than I recommend emulating the anniversary edition as it doesn’t require having a second player to play (or if you’re willing to shell out enough money to get a DSI that had four swords downloaded on it before the DSI shop closed that works too, just be aware that completely resetting the console will get rid of the game as well, which is why I have the DSI of some 8-year old named Deigo).
For Four Swords Adventures I’d recommend simply playing on original hardware as it also doesn’t require a second player, and you only need the GameCube and a regular controller.
If you simply have to play with friends than that’s gonna be an issue unless you’re willing to pay a decent sum, as using a link cable on emulation is incredibly finicky, to the point where I haven’t even been able to successfully do it. Four swords itself barely works on the original GBA, so playing that with friends is pretty much impossible unless you want two buy TWO whole DSIs off of eBay.
FSA is a bit easier as you only really need the game itself, 2 cables (which are pretty cheap all things considered), and two GBAs. Any model of GBA will work except the Game Boy Micro, and honestly that’s the only way I’ve been able to play either four swords game with friends.
It’s not cheap at all, so I really recommend against playing unless you’re a collector like me. But if you just wanna play by yourself it should be fine.