President-elect Donald J. Trump is planning a string of executive orders during his first days in office, including one to strip job protections from career civil servants, his top policy adviser told Republican members of Congress on Sunday, according to two people briefed on the matter.

In a phone call with a few dozen Republicans on Sunday, Stephen Miller, Mr. Trump’s incoming homeland security adviser and deputy White House chief of staff overseeing policy, laid out the broad strokes of what Mr. Trump is planning on energy, immigration and federal workers. The call was reported earlier by the website Punchbowl and confirmed by two people briefed on the conversation.

A Trump spokesman did not respond to an email seeking comment.

Mr. Trump has indicated he plans to sign roughly 100 executive orders in the initial days of his presidency, with a number coming within hours of his being sworn in on Monday.

Among them are substantial actions to reshape the federal bureaucracy’s workplace rules, which are in line with various promises that Mr. Trump made on the campaign trail.

Mr. Miller described, while providing little detail, executive orders to undo actions taken by President Biden to institute “diversity, equity and inclusion” measures in federal agencies, and to roll back protections for transgender people receiving some government services.

Mr. Trump also plans to reinstate an order he issued during his first term to create a new category of federal workers, known as Schedule F, that would lack the same job protections enjoyed by career civil servants, who are supposed to be hired according to merit and cannot be arbitrarily fired. That would allow his administration to shift large numbers of federal workers into a new status over which it could keep a much tighter rein, including the ability to hire and fire them more easily. The order is significant as Mr. Trump and Mr. Miller have a deep hostility toward large portions of the federal bureaucracy, which the president-elect often derisively calls the “deep state.”

Mr. Trump is also planning a string of orders related to energy policy, much of which arise from pledges to encourage offshore drilling and end the electric vehicle tax credit, as well as stop spending on Mr. Biden’s climate policies.

And on immigration, as The New York Times has reported, Mr. Trump is planning to designate drug cartels as “foreign terrorist organizations”; declare a border emergency to allow him to go around Congress and surge money and potentially military resources to the border; and declare a public health emergency to essentially seal the border as the administration did during the coronavirus pandemic. He also is expected to curtail asylum grants and step up detentions and deportations.

Mr. Miller has been leading the executive order process throughout the transition, aiming for as much secrecy as possible and only opening the aperture internally as time went on so that various agency heads could see some of the work. He has been using a team of lawyers to vet them.

At his rally at the Capital One Arena on Sunday afternoon, Mr. Trump told the crowd that the executive orders would make them “extremely happy.”

He said he had beaten back efforts by some advisers to delay his Day 1 executive orders, saying he wants to give the country a massive first day and first week in office filled with activity.

Mr. Trump also said he plans to quickly release the classified files related to the assassinations of John F. Kennedy, Robert F. Kennedy and Martin Luther King Jr.

And he previewed coming clemency grants for people convicted in connection with the attack on the Capitol by a pro-Trump mob on Jan. 6, 2021. He referred to them as “hostages,” as he has throughout the campaign.