In later versions, Oracle Database has gotten better at chaining within a block if there's enough space. I've discussed this in detail at: https://asktom.oracle.com/pls/apex/asktom.search?tag=table-255-columns-row-chaining
Chaining within a block often won't appear in row chaining metrics, which could go some way to explaining the big difference.Can the diff in chaining be explained by which columns are being referred to in the update statements?
That may also play a part here - which columns you change, how often, and how much space is available in the block at the time all play a role.Can PCTFREE settings have any positive impact on chaining with wide tables?
It could have a positive impact, it could have a negative impact...Are there any other tactics you can suggest?
To do what specifically?
Unless you have a performance issue which you've found is primarily caused
by row chaining, I suspect there are other optimizations you could make to the system which would have bigger benefits.