If anything other than tilemaker is chosen for #2, the osm data needs to be in a postgis database.
The three options are
something that abstracts away tagging like imposm or osm2pgsql ClearTables
OpenStreetMap Carto's 4.x schema
osm2pgsql default
Abstraction is normally an advantage, but when aiming to be a stylesheet fairly close to the data and tagging like osm-carto is, it's a disadvantage. It doesn't make sense repeat the problems of osm2pgsql default, so osm-carto's transforms are a good option. This also allows the same DB to power both styles, which is a huge advantage.
If anything other than tilemaker is chosen for #2, the osm data needs to be in a postgis database.
The three options are
Abstraction is normally an advantage, but when aiming to be a stylesheet fairly close to the data and tagging like osm-carto is, it's a disadvantage. It doesn't make sense repeat the problems of osm2pgsql default, so osm-carto's transforms are a good option. This also allows the same DB to power both styles, which is a huge advantage.