You can not twin fireball, but you can quicken it for the same cost, and then cast it with your bonus action again.
You can also twin powerful single target spells, like the buffed haste, hold person/ monster, and later disintegrate.
If it works like in tabletop, the other metamagic options can also be quite good.
Subtle spell makes you immune to being counterspelled for example, and some of the end bosses seem to be spell casters.
Or heighten, which can make it much easier to actually hit with spells
