The wall is a force multiplier and is not going to keep illegals from crossing the border by itself. It’s purpose is a deterrent and to slow egress down so the BP can arrest them. Any unmanned wall is useless.
Absolutely...building the wall is just the first step, to be followed by manual & electronic surveillance of the entire border, followed by removing incentives to hire cheap illegal immigrant labor.
But do not forget that majority of illegals arriveon jet planes and overstay their visa.