You are confused. Or trolling, not sure which.

Hexadecimal strings are just numbers. Txids, npubs, nsecs, are all just hexadecimal strings, which are all just numbers.

You can get theoretically any number as a txid, or an nsec, or an npub. If you use a txid "as" an npub, you will not be able to work backwards to the nsec. If you use a txid as an nsec, that should work fine, but your nsec is pretty insecure so that's not recommended.