The pool phase will be extended by a week, ensuring teams will have at least five days to prepare for all matches, while squad sizes will be increased from 31 to 33 players.
PRPW said that since 2003 the scheduling of Rugby World Cup matches has "brazenly prejudiced Tier 2 nations" and said the latest reforms are long overdue.
"This is a significant step towards a tournament that fully respects the ideals of fair play, and it will make a great difference to the Pacific Island teams," said former Manu Samoa international and PRPW CEO Dan Leo.
"We fully support the extension of the RWC 2023 schedule and believe that there will be a tangible impact on the competitiveness and quality of the tournament."
Pacific Rugby Players Welfare detailed the way in which Tier Two nations have been consistently disadvantaged in its submission to World Rugby's governance review last year and called for standardised rest days for all World Cup participants.
At the 2011 World Cup, Samoa had only three days in between their first two pool matches against Namibia and Wales and four days off between their final two matches against Fiji and South Africa.
In 2015, Fiji, Samoa and Tonga all had to cope with a five day turnaround during the pool stage, while at the last World Cup in Japan the Flying Fijians were upset by Uruguay just four days after their tournament opener against the Wallabies.
CEO Dan Leo said the move will ensure a more level playing field for all competing nations but said it was "telling" that the tournament is now being extended only after Tier One nations experienced at least one short turnaround during the 2019 World Cup.
"Tier 2 nations have been crying out for better treatment for nearly 20 years, but only now that Tier 1 nations are experiencing similar, unfavourable conditions are World Rugby taking this matter seriously. It is symptomatic of rugby's treatment of Tier 2 nations."
PRPW also expressed surprise at the timing of the announcement, saying it was told explicitly by World Rugby three weeks ago that it was "not possible" for the tournament to be extended beyond its traditional six-week window.