UPDATE on 20 Million Records Transaction or not?

Hello List,
PostgreSQL 11.8 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (R
ed Hat 4.4.7-23), 64-bit

I am planning an update on a table with 20Million records, I have been researching the best practices. I will remove all indexes and foreign keys prior to the update, however I am not sure if I should use a transaction or not.
My thought process is that a transaction would be easier to recover if something fails, however it would take more time to write to the WAL log in a transaction.

Would it make sense to make a back up of the table then execute update without a transaction? How would you guys do it?

Thanks,

Jason Ralph

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