My idea with a border fence is similar to my approach to home security. A dedicated thief could break into my home at night, but it is clearly much harder to get into my home than other homes. I don’t expect many thieves to try hard enough to find out what happens if they do get in. At some point, they might even decide not to burglarize homes.
Similarly, if we make the border moderately secure and then enforce immigration law uniformly against on those who do make it in, it won’t be worth the effort to try to cross our border illegally. Force them to make long tunnels and then destroy the tunnels as they are discovered. At some point, it will become easier to just follow the law.
Jail those who continue to hire them.