Option 1 is correct. Option 2 mixes up both the production of lactate (anaerobic) and the clearing of lactate (aerobic).
The rate of lactate accumulation is absolutely important, but it’s simply a function of how your aerobic and anerobic energy systems interact.
I’m not clear yet on how this is measured in a lab. I’ve got a decent high level view of what types of adaptations you get from different training, but I still have a long way to go to understand why training in X zone causes Y adaptation. I think it’s easier to understand why Y adaptation improves either vo2max or vlamax.
And on your last paragraph, I think you’ve got the right idea on mechanisms. Keep in mind “removal” is essentially converting lactate into actual power output. So the more lactate the aerobic system processes, the faster you can go aerobically. But yes, your assertion that removing more lactate would result in a higher threshold is spot on.
On the training to do, I think you have it backwards. Endurance to improve your Vo2max, and SS to lower Vlamax. There’s some overlap on some of the training effects. Here’s a screencap from the webinar I linked earlier in the thread about expected adaptations in each zone.
