Thank you Ronnie, seriously helpful!
For anyone else reading this I just want to note that savings to the tune of £18,600 is also sufficient (you must have the money in an easy access bank account for 6 months prior to applying; and it can be either joint money between you both, or just from one of you).
My main concerns stem around proving that we have cohabited for two years prior to applying. We will need 6 formal letters addressed to us, over the course of those two years, but I haven't been able to receive any mail here and due to practicalities we live in an airbnb. I fear that airbnb records are not going to be hard enough documentation for the government, if they are feeling strict.
Also wondering at what point an Argentinian is legally allowed to work in the UK (upon approval of the spousal visa).