ΔE 27.1, loose: different enough that you should pick on purpose. Heirloom Gold is noticeably lighter than Balthasar Gold.
Can I use Heirloom Gold instead of Balthasar Gold?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Heirloom Gold is noticeably lighter than Balthasar Gold.
Can I use Balthasar Gold instead of Heirloom Gold?
The same difference applies the other way round: Balthasar Gold is noticeably darker.
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.