The move follows discussions between the tour and top players such as McIlory and Tiger Woods in the wake of the emergence of the rival, Saudi-backed, LIV Golf tour.
"These smaller, designated event fields will not only deliver substantial, can't-miss tournaments to our fans at important intervals throughout the season, but they will also enhance the quality of full-field events," PGA Tour Commissioner Jay Monahan said in a memo to tour members.
"Together, this approach provides a schedule that is cohesive, compelling, consequential and with clarity for fans, players and sponsors alike," he added.
Fields will be restricted to 70-78 players drawn from the top-ranked on the previous year's tour points list along with those in the best form in that year's campaign.
Although no decision has been taken on what tournaments will be in the new format, all will be without a cut after 36 holes, meaning the players will compete on all four days.
The changes will not impact the majors, the Players Championships or the FedExCup playoff events.
The top 50 players from the previous season's points list will qualify for the events along with another ten players from the current season's list and the current season's tournament winners.
Unsurprisingly McIlroy, who has championed the PGA Tour in the face of defections to LIV Golf, gave his full backing to the changes.
"I love it. Obviously I've been a part of it and been in a ton of discussions," he said ahead of Thursday's Arnold Palmer Invitational at Bay Hill, Orlando.
"I think it makes the tour more competitive... I'm all about rewarding good play...I want to give everyone a fair shake at this, which I think this structure has done. There's ways to play into it," he said.
McIlroy said the aim had been to ensure that players in form still had a chance to take on the established elite.
"It's trying to get the top guys versus the hot guys, right? I think that creates a really compelling product. But a way that you don't have to wait an entire year for your good play to then get the opportunity. That opportunity presents itself straight away," he said.
"You play well for two or three weeks, you're in a designated event. You know then if you keep playing well you stay in them.
"At the end of the day we're selling a product to people. The more clarity they have on that product and knowing what they're buying is really important. It's really important for the tour. I think this solves for that," he said.
Push from LIV
American Max Homa, who won the Farmers Insurance Open in January, said the changes to the tour wouldn't have come so quickly had it not been for the emergence of a rival tour.
"I don't think we would be here this soon without LIV, but I would hope at some point we would have looked at this and said, 'Hey, there might be a better way to do it,'" he said.
"It does seem like the emergence of LIV forced us, as players and the executives of the PGA TOUR, to just look at the product," he added.
"They (LIV) don't have to deal with tradition. So they got to set out a piece of paper and say, What should we do? And I think one of the things that they have that's great, that this will provide now, is a guaranteed product. You know who is going to be at each event," he said.
"I think that's important for fans."
