The Republicans have said they won't do anything about the border b/c it might help Biden, right now the Senate is considered a bipartisan bill with the tough controls.
Trump didn't do anything about the border, the wall is a joke (go look at the geography of the southern border, any wall will have lots of gaps, and gangs would have no problem taking down a section at night, flood that region with immigrants, and then repeat elsewhere a week later - it's not the Great Wall of China, in fact, sections have collapsed.
Any President will be hamstrung by existing law, Congress has to pass laws to tighten asylum rules, fund more judges to process immigrants faster (Biden has doubled funding but limited by Congress), fund tracking illegal immigrants who overstay their VISAs, set up guest worker programs (farmers are desperate), improve legal avenues (want highly educated and trained immigrants) to citizenship, resolve the DACA issue, make service in armed forces automatic qualification for citizenship, etc.
Biden is ready to deal, McConnell is willing to work with him, but the MAGA branch of the party wants chaos, they put Trump over the country.
If Trump is elected the country will go to hell, four years of nonstop chaos (since he'll hire incompetent people, everything will be challenged in court and he'll lose, so total gridlock), a disaster for the world (Putin knows Trump is a fool and will take advantage of him, same with Xi) - and we'll deserve the consequences.