Abolish the ATF, IRS, and Federal Reserve
I’m not sure how much difference abolishing the ATF would do. I’m assuming that the intent is to weaken investigation and enforcement of some or all of the regulations which the ATF specializes in (federal ones relating to Alcohol, Tobacco, Firearms, and Explosives) if not neutralizing them outright. In practice it would just end up dumping those cases on other agencies (I suspect mainly the FBI) which don’t specialize in them. This might just end up slightly weakening everything across the board rather than those things specifically.
Abolishing the IRS would make paying taxes entirely voluntary. I’d assume that some other agency, likely the Treasury, would take over the collection. Not sure if this is a case of “not paying taxes is unthinkable”, “it should indeed be voluntary”, “ban all taxes” (while not understanding how the government pays for things) or simply not understanding what the IRS does.
Abolishing the Federal Reserve without replacement would be a return to economic instability of the likes which few people alive have seen. It’s been a mixed bag - boom/bust cycles are kept from wreaking as much havoc as they would otherwise, more so before the Glass-Steagall Act was repealed in 1999, less so now. But the methods of doing this were often questionable, even to the point of effectively rewarding corporations for making bad decisions. The Federal Reserve probably does need to be better regulated or replaced with a new government entity which does its job better (“The Fed” is currently semi-autonomous). Which will probably not happen any time soon, but just getting rid of it is probably worse than leaving it alone for now.