Saving document flat vs object

Hi,
I’m working on a system that integrates with a trading system and I need to save the data/objects from there as is without touching them in my MongoDB,
I’m wondering which approach will work better with Mongo in the long term, for a lot of writes, reads, and aggregation. ( of course, will need to add indexes where I will want to read efficiently).

Approach 1:
uniqId
createdAt
updatedAt
field_a
field_b
field_c
field_d

Aproach2:
uniqId
createdAt
updatedAt
data(object with everything)

Does any of the approaches have an advantage over the other? regarding performance and scale also

Please see