This is way way in to the weeds of LoRaWAN and is totally transparent to the user and probably 95% of implementers wouldn’t know it happens. The Semtech website will have papers on this, but along with your ideas about changing the bandwidth and trying to create an RF test environment are a bit early in the knowledge acquisition process - like figuring out the best compounds of rubber to make your tyres on your unicycle when you have still yet to ride without stabilisers. The end effect is you don’t ever get to ride a decent bike because you’re too bogged down in the details.
Given that there is currently a roll out of 150,000 meters in a central part of the UK using LoRaWAN as an example, you can be assured that almost all the parts are there to move data and from reading your prior post I suspect that some refinement of the payload will go along way to make it be a better fit for off the shelf technology which protects such a project as someone else can pick it up if you are doing something else.
The majority of power monitoring accumulates usage data in to total consumption since last “reset” so that if any packets are lost, the overall use is still known even if how it was used over a period of time may not be apparent.
The mechanics of messing with mains power to steal small chunks - like having a single light on but then bypassing the meter for the duration of boiling some water - are way way beyond the vast majority of people and are stupid easy to detect. As well as running a meter upstream of the distribution point and see how the totals compare, the profiling of a normal household is easy to compare to to one that is more erratic and then some actions could be taken, which may well include more frequent uplinks for that meter. Power use tends to be stepped - a household runs at say 500W background use, steps up to 3kW while using a kettle (500+2500) and then back to 500W. In these data scenarios I can send a new value with a start time, using the difference between times & power to make the numbers smaller. Unless a five year old is flicking a switch on & off, most of the time the use is pretty stable.
If you read my answer to another typical application issue here you will see that you can also code in overlapping data or a replay. In this situation you could store a lot of instantaneous readings on the device that can be recalled if an anomaly is detected. However I wonder where this paranoia comes from - providing power to a community that may be withdrawn if they collectively allow some of their members to steal it should suffice rather than have a massively over engineered / complicated solution put in place. If a simple system is deployed and the meters at the branches to the spurs identify any misuse, it then becomes worth extending the system to capture such data.