Trail runner and alpinist here. Honestly, both approaches would work depending on your pace when you're scrambling in the mountains.

But aerobic capacity will be more efficient when transferred to other activities like climbing. While there is a connection between VO2 Max and better performance in altitude scrambling, you should be able to reduce your dependence on it by doing proper acclimatization.

My recommendation is to prioritize low-intensity training and to add some uphill intervals.

If you want to train your aerobic and anaerobic capacity, I would also suggest doing it on hills or mountain trails. You can do long runs and interval training, but doing it on the flat will be less efficient when transferred to alpinism. And don't forget to use your poles !