Speed: Metafields import speed doesn’t depend on Metafield count anymore. Even for 100 Metafields per item, it will import as quickly as with no Metafields.
Delete: You can delete Metafields for items just by clearing values in that Metafield column, and importing.
Set type: Metafield can have “string” or “integer” type, which is now auto-detected from Excel cell type, and set correctly when you do the import.
Read more: Metafields template documentation