New FIFA rankings

Finish first or second in our Nations League group and we are second seeds in the qualifiers proper, finish third and we are third seeds, as well as being relegated.

FIFA rankings have nothing to do with the Euro qualifying draw. That said, the next World Cup qualifiers will probably be drawn next summer, so our performances in the Nations League will also be important to ensure continued decent rankings for that seeding too. World Cup qualifying will probably be drawn based on FIFA rankings.

There will be playoffs. But you are correct in that the countries involved will be coming from their Nations league placings and not third place in the qualifying group.  

Also important to note that under the old system, the best placed 3rd team with the highest points qualified automatically (Turkey as it turned out), the remaining eight 3rd placed teams went to playoffs to qualify for a total of 23 spots (with France)- so 4 playoff spots were available from 9 groups and 1 extra automatic place.

This time, no team qualifies automatically, but there are 10 qualifying groups, so 20 teams go through from those (1st & 2nd in each group). There are also 4 playoff spots available through the Euro league rankings, but one of those spots will be allocated to League D. We won't be in that, so that leaves 3 spots. 

The extra qualifying group theoretically weakens some of the groups (strong teams divided by 10 instead of 9), but against that, there are less spots for us to play for if we do get to playoffs, though again, theoretically, they should be against slightly weaker teams. 

The more I look at it, the more I'm convinced that this format is to give an Italy or a Holland a 2nd chance should they slip up in qualifying like they did for the WC, but this is obscured by the absolute genius of allocating a league D team a place. This creates the illusion that anyone nearly has an equal chance of qualifying, when in fact, the playoff spots available to us have reduced from 5 chances from finishing 3rd  (4 playoffs & 1 automatic place) to 3 chances, albeit, in theory, those playoffs might be against slightly weaker teams than would have been the case in the old system. 

That is unless anyone is optimistic enough to think that a man who withdraws central midfielders & replaces them with out of form wingers in central midfield in a crucial qualifying game can guide us to 2nd place. 

Only 8 years late, but still...