ΔE 17.9, loose: different enough that you should pick on purpose. Isoindolinone Yellow is much more saturated than Lugganath Orange.
Can I use Isoindolinone Yellow instead of Lugganath Orange?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Isoindolinone Yellow is much more saturated than Lugganath Orange.
Can I use Lugganath Orange instead of Isoindolinone Yellow?
The same difference applies the other way round: Lugganath Orange is much more muted.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.