After the decision to start the UEFA Nations League, UEFA explained the planned system of competition.
In the UEFA Nations League, the 54 member associations will be divided into four groups based on coefficient rankings. These groups will then be further divided into playing pools of either three or four teams. The teams in each pool play each other home and away between September and December of the season in question, with the group winners either qualifying for the final four competitions or gaining promotion. The bottom sides face relegation from their division.
The bolded part is most important when it comes to Macedonia. If the 54 teams are divided into 4 groups, the groups will be with 13 or 14 teams apiece. In the coefficient rankings, Macedonia is currently 42nd, meaning there are 12 other teams below them. If Macedonia ends up in the last group, it will end up with the likes of Andorra, San Marino, Faroe Islands, etc.
In addition, the UEFA Nations League will provide teams with another chance to qualify for the UEFA EURO final tournament. Four teams within each group, who have not already qualified for the finals, will qualify for the play-offs in March 2020 with one team from each group joining the 20 teams who had qualified via the European Qualifiers.
Following the acceptance of the resolution on national team football at the XXXVIII Ordinary UEFA Congress in Astana on 27 March 2014, UEFA and its member associations will continue to work together to elaborate and implement the UEFA Nations League. It is envisaged that the first UEFA Nations League matches would take place in September 2018.
What are the advantages for national associations and teams?
National associations and coaches in consultations with UEFA revealed that they feel that friendly internationals are not providing adequate sporting competition. The UEFA Nations League creates more meaningful and competitive matches for teams.
Top teams can also aspire to take part in the final four competitions, a new top-level event.
For middle-ranking and small nations, the UEFA Nations League will provide an extra way to qualify for UEFA EURO final tournaments. Lower-tier nations − the bottom 16 in rankings − are now guaranteed one of the 24 qualifying slots for UEFA EURO.
While the UEFA Nations League will replace most friendly internationals, there will still be space in the calendar for friendlies, especially for top teams who may want to play teams from outside Europe as they will be in groups of three teams.
Associations and teams benefit from clarity of the fixture calendar, and there is now a clear buffer between the end of UEFA EURO and FIFA World Cup, and vice-versa, and stability of income.
above text is from uefa.org