Soldato
Yeah, I agree. It really does depend on how serious you are/willing to be and where you want to take your cycling.
Having the power meter is one expense but then WKO4 purchase and the time investment in learning is very high on both counts, or also, a coach can be an expense outlay as well to have that expertise without learning yourself.
You could easily have your TTE calculated though from turbo and outdoor rides. It is a model so will use the data you do have to estimate all of these metrics. Like any decent metric based system though, the more data you have and the more accurate this is factors greatly on how useful and accurate the modeled figures are (and you need WKO4 for it, did I mention it's expensive? )
Certainly interested to learn more, although I do think once you get into the WKO4 metrics you're overcomplicating things for most amateurs. I think it's alimportant to remember that increasing FTP/mFTP should be a "side effect" of your training rather than the goal itself. I think where mFTP can be a good metric is that a lot of training doesn't increase FTP itself but does increase the % of FTP you can sustain. It can be really hard to track that progress with FTP alone as a metric.