This is all "I think", so no better than the multiple opinions you already have ..
If you have 2+ cars you can have them on the same account, or get one "moved" to a different account.
If you self referred the 2x 1,000 Supercharge miles will be shared between both vehicles if on one account, if in spearate accounts then split so you would be having to use them up seaprately, within 6 months. I'll put change of 0% on Tesla doing that right at when they split the accounts!!
I have his/hers cars, and one for Sprog, and PowerWall, all on one account, so the rest of this is with that perspective:
2+ cars on one account you can "swipe right" for the other vehicle(s) (and PowerWall etc). We definitely use that - I get a holler from the other room "
I'm leaving shortly can you put climate on my car ..." (no indication which car she is taking .. but ...
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Not sure how (if?) the APP would handle two separate accounts.
TeslaFi allows two cars to be on a single "display". I don't think it matters if both on same Tesla account (if there are multiple cars on Tesla account you get a picklist to choose which car is being logged - indeed you can chop-and-change and thereby completely screw up your historical stats data ...), or aggregate from two separate Tesla accounts. Either way you need two separate TesalFi accounts (and then "join" them).
TeslaFi for 2 cars is moderately pants. After it times out it reverts to Car One. So if you view Car 2, make a coffee, come back and press "Next day" or similar you revert to Car One. Making "current car" sticky would be better. It does do some "combination" things - combined heat-map for travel for example
TelsaFi doesn't handle 3+ cars at all.
If you or wife are having an affair then maybe separate accounts?
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