The two are among 11 defendants accused of taking part in a plot to replace Moise by sending a team of Colombian mercenaries to kill him in his Port-au-Prince residence.
Of four who have so far been sentenced in Miami, all have received life.
Moise was shot down in his bedroom during a night-time raid, and his death left a political vacuum during which alliances of violent gangs have expanded their territories and are now estimated to control most of the capital.
The ex-informant, Haitian-American Joseph Vincent, had pleaded guilty to helping the plot by providing political advice and meetings with community leaders.
According to a court document, he had masqueraded as a US government official.
The same day, Florida resident Frederick Joseph Bergmann Jr also pleaded guilty to charges in the case, including submitting false or misleading export information.
Bergmann Jr was arrested alongside three other Floridians a year ago, at which time US authorities said he had helped fund the mercenaries' Haiti lodgings and helped ship bulletproof vests to Haiti by falsifying export documents.
They had said he could face up to 20 years in prison.
A separate investigation is being carried out in Haiti, with the judge calling to interview figures such as Prime Minister Ariel Henry, Moise's de facto but unelected successor, and his widow Martine Moise.
In the years since Moise's death, violent gangs armed with guns believed to be largely trafficked from the US, have massively grown their power, their turf wars driving a humanitarian crisis and hundreds of thousands from their homes.
Earlier on Friday, the United Nations said January was Haiti's most violent month in over two years, with more than 1100 people killed, injured or kidnapped.
Anti-government protests broke out in the days leading up to February 7, the day by which Henry had promised to step down, though he later backtracked saying security must be re-established for free and fair elections.
Haiti's last elections took place in 2016 and its last senators' terms expired in January last year.
