Big Sur updater vs full Big Sur installer

I have four Big Sur installs (main internal disk, two Carbon Copy Cloner backups and one "clean" test drive) for Mac mini 2018 (and also Mac Book Pro 2014 in the household with its CCC backup).

CCC can make bootable clones but with Big Sur it now must erase the target drive when doing so and it takes time with large data volumes.

So in the past I have updated only the main internal disk and maybe the test drive and used CCC for incremental data volume backups (so the backup system volumes were not updated which seems not kosher...).

This time I have planned to download the full Big Sur 11.5 12.6 GB installer once instead separately downloading just the 2.93 GB update as many as 6 times for each Big Sur update (6 x 2,93 = 17,58 GB + several failed downloads that are a nuisance nowadays...).

Then I can be pretty sure how long each update will take because sometimes the download is very slow.

Questions:

1. I guess the end result with the incremental macOS update vs applying the full installer is the same?

On the other hand, in the past some folks have argued that the old-style "Combo" OS X updaters might be more reliable than smaller incremental point updates. I guess the full installer is in effect a Combo updater in this respect?

2. Does it matter whether I make a bootable flash installer and apply it or run the full installer while booted from the volume I intend to update?