Organisers promise "more music" as a result, with artists being given full creative control of their performances.
Prizes like best British video and best international group have been cut, while the outstanding contribution award has been retired for 2020.
Despite press reports earlier this year, gendered awards for best male and best female will remain.
The changes come after several years of falling ratings. This year's ceremony, which saw performances from Pink, Dua Lipa and George Ezra, was watched by 4.1m people, down 400,000 from 2018.
The decision to scrap some of the awards makes for a more streamlined show, but fans of BTS are already angry about the loss of best international group.
The biggest change, however, will be in the performances.
The Brits say they will "hand the stage to the artists booked to perform on the night without imposing any creative limitations".
The idea is to create more viral moments - like Kanye West's performance of All Night on a stage crammed with British rap talent, or Adele's simple but effective rendition of Someone Like You.
Of course, the most surefire way to go viral is to fall off stage like Madonna in 2015, or one of Katy Perry's dancers (visually impaired by having a house for a head) two years later.
But giving artists creative control could give ITV's censors a major headache.
Earlier this year, Brits organisers stopped The 1975 from performing Love It If We Made It after they won best British group, due to lyrics about drug abuse.
"There were a number of complications," said the band's manager Jamie Oborne, "which included us not wanting to have the words changed and ITV not wanting Matthew shouting [swear words]."
Under the new system, the performance would presumably be allowed to go ahead.
Winners on the night will receive the classic Lady Britannia Brit statuette, which returns after nearly a decade's rest. Recent years had seen a bespoke "remix" of the design, by artists such as Damien Hirst and Anish Kapoor.
And fan votes have been scrapped altogether - meaning an end to boy and girl-bands dominating categories like best single.
This year, all awards will be decided by a 1,200-strong "official voting academy", made up of experts from all areas of the music industry.
That's not necessarily a positive move, however, as fan votes were often the only way for phenomenally successful acts like One Direction, Girls Aloud and Little Mix to gain recognition.
Brits chairman David Joseph explained the changes, saying: "We will be putting creativity, British culture and exceptional performances at the heart of the show to make Brits night a world class celebration.
"The awards should be a global platform for the artists of the year to create moments that live beyond the night itself. We are looking at everything to put on the best possible show."
The Brits launched in 1977 to mark the Queen's silver jubilee, but didn't return until 1982 - which means 2020 will be the 40th ceremony.
Organisers say the event, at London's O2 arena next February, will mark the anniversary by paying "tribute to to many unforgettable Brits moments that are now part of a rich and much loved heritage."