AI has the ability to spawn ELIs, Grenadiers, Old Guards, Horse Grenadier Guards and Siege Artillery in low tier cities.
But that also means that their taxation will be heavily affected.
After 2-3 more runs in the 1815 conquest, I had realised that they had 2 main armies.
One in Iberia and one in Central Europe.
So the reason why without even defeating the Spanish and the Portuguese completely, they disband their troops there. And sadly, this is actually a balance move to make things well, balanced for both sides.
However, because of disbanding them, they can respawn them at Central Europe which easily helped defeat Bavaria (whom I had to always declare war whenever the Prussians capitulate in order to make sure they are contained and also avoid a major defeat).
So the French AI here has overpowered armies but also has major setbacks in terms of population size (because if it had continued on, it would mean France can push back Russia and Scandinavia while its Iberian troops invade Iberia and make its way to the Americas which will result in a pretty short game.)
I had never successfully had a long term Coalition 1815 game due to France already at Moscow by turn 40 although I see that their Iberian Front is being retaken by Spanish and Portuguese troops.
In conclusion: AI is semi OP. Always play as the French Eagle if you don’t want to have a hard time.