This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
璁 combines 王 (jade) with 悤, which likely contributes the sound. The exact historical development is uncertain.
The left side 王 suggests jade or a precious stone, but the overall meaning is obscure. Picture an ancient jade artifact whose purpose is forgotten.
For ソウ, imagine a soul (ソウ) trapped inside a mysterious jade stone: soul -> ソウ, and the jade 王 holds the sound.