Any effort longer than about 45 seconds (at a guess; it probably varies from rider to rider) will be a mixture of anaerobic and aerobic, with the anaerobic component decreasing the longer it gets. A 1 minute effort will have a big anaerobic component, a 10 minute effort will be mostly aerobic with maybe 10% anaerobic contribution, a 60 minute effort will have virtually no anaerobic at all.
(Quote from Coach Chad on the podcast: “Recognise the fact that even short efforts are very aerobic, and the bigger your aerobic engine, the better off you’re going to be.”)
So the longer the sustained efforts you want to do, the more you train your aerobic system with sweetspot, threshold, and vo2 max intervals.
If you do crit or road racing with short hills that involve following attacks, or pushing hard for 30 seconds over short rises, then you’ll want to add more zone 6 / anaerobic work into the mix.
The clever thing about Trainer Road is that if you follow the plans, you don’t need to worry about it too much. TT plans have mostly aerobic and Crit plans have more anaerobic. It’s all done for you.