I would not join TCX if you are heavily into the idea of an early command. When I joined there were folk who got a command in 18 months, between then and now, I have seen people wait any number up to 15 years. A lot of this is purely luck, being on the list in right place and right time when the company does one of its periodic expansions. Right now is great for a number of SFO's. Next year, who knows what world event will blow the company finances of course again and down the snake the new commanders might come. TCX is prone to that sort of instability.
All I'm saying is choose tcx for the lifestyle of charter and holiday long haul, if that is your thing. Personally, having looked at all the options globally, there is nothing else which is so much better that is was worth leaving for.