What happens if you upload difft maps over preloaded maps?

[Wesley]

For me this question is related to the Quest2, but perhaps other Garmin owners can provide their expertise with how Garmin does things.


The new Quest2 has N.America preloaded, but it also has "140 MB supplemental map storage is available for downloading map detail from other MapSource products"

What happens if I upload a newer (or older) version of Los Angeles into the unit? Does it follow, display, and auto-route via the preloaded maps or the ones I upload?

Have there been other Garmin units in the past which have had preloaded maps AND allowed uploading of additional maps? How do they react to this scenario?
Thanks

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