the 2021 battery should be 75kWh and the newer ones should be 82kWh. What gives?
2021 model year is when packs started switching to 82.1kWh (actually closer to 81kWh usually). Before that they were 77.8kWh. The first 2021 models with 353 miles (not 358) of range had 77.8kWh packs but started switching to the big packs mid-2021. (Performance 2021 always had the new pack type.)
Teslafi shows my charge efficiency is 94% over 2 years
I would not trust TeslaFi. It's not correct. (You can dig into the TeslaFi documentation to determine why. I think one reason is that it may report the kWh added in the car for "energy to the pack" which is not correct - it's well known that this number is 4.7% too high (1/0.955). But there may be other reasons; I don't use TeslaFi so I have no idea at all. TeslaFi is just a tool; it's not intended to be accurate.)
The answer to your question is as above - this is a wall-to-wheels number. Roundtrip losses are around 10%. The EPA results show about 11% (they provide charging event energy, and the energy metered during a discharge of the entire pack to empty - this gives you the losses). Note these losses depend on the charging setup but at least 240V/32A is assumed for these results.
And yes, the EPA tests get some very high numbers for city and highway, since they run them at very low speeds ( the highway cycle (HWFET) is quite slow for example, average speed is 48mph).
It's a complicated topic which you can dig into if you wish. All the documents are here; currently the website is down (this has been happening frequently lately):
Basic Search | Document Index System | US EPA
You'll find the charge event energy and the discharge energy there. Your calculated numbers are pretty close to the charge event energy, by the way.
You can also go here, this is less useful though. However, it does allow you to derive the scaling factor used (ratio of adjusted to unadjusted economy).
Fuel economy Fuel Economy Datafiles (1978-present), Fuel Economy Guides (1996-present)
www.fueleconomy.gov
This has all been extensively documented on TMC in the past - you just have to search with the right keywords, and do some research.
Currently Tesla is using an adjustment factor of about 0.747 for the Model 3 as I recall. Before the heat pump it was closer to 0.703 (but there were a couple of exceptions).
Not that fun, tbh.