Each training building (Barracks, Stable, Archery Range, Siege Workshop) has its own queue, so all of them can train at the same time. But each building runs one task at a time, and training new troops and upgrading old ones share that queue.
Other rules:
- Training capacity sets the batch size; training speed sets how long it takes. Bigger batches take longer.
- When the timer ends the troops are Ready to Claim; they only count once you claim them.
- Only Universal Speedups and Training Speedups work on training.
- Upgrading converts existing lower tier troops, so they vanish from your count until you claim the upgrade.
- Civilization special units only exist at T4 and T5.
Before logging off, set each building's batch to last until you are back.