I think that your question has not gotten responses because others may not want to put their neck on the line by recommending the campaign game because some have had problems with it. Let me summarize my experiences which has been to complete two full games.
* the game stretches your computer system resources. My first full game was on a Windows 7 desktop system and I had fewer challenges than when I played it on a Windows 10 laptop.. As the game grows in size there is more potential for problems such as system crashes. There have been posts on how to alleviate this and to summarize; if you shut down all unneeded processes, disconnect from the internet and shut down your virus scans, these problems are reduced. Always check the option for saving at the last 6 turns and if you have the available storage, choose the 9 turn option. In my last game, I had a problem late in the game when I was marching Davout down the east coast of England and every time I tried it, the system crashed. I had to go back 3 turns and change his direction of march and was able to proceed past that one problem and finished the game.
* If you select options for higher AI setting (more time for planning its moves, turn on realistic supply, historical supply and historical force pools, the AI will give you a challenging game. It is not perfect in its decisions and may throw forces at you piecemeal later in the game when its forces are depleted, but this will balance against the settings to give you a challenging game.
* the game will naturally migrate away from a historical turn of events. Preconditions for scripted historical treaties etc. have very specific conditions and you can run into catch 22s which make playing a historical game difficult. For instance, to dissolve the Holy Roman empire and form the Rhine Confederation, you must own Ulm. But if you are too fast to sign a peach with Austria, you may end up giving back Ulm to the Austrians in your treaties and then be unable to select this option to dissolve the Holy Roman Empire. If you want to keep the game on a historical pathway, read preconditions carefully.
The challenge in the long run are in the victory conditions. As the French player you will need to capture Moscow, Madrid and London. This can make the game very challenging strategically. Other challenges in this game include:
1. Supply when invading Russia, as Russian units will try and cut you off.
2. Diplomatic advances to secure use of the Spanish, Dutch and Danish navies.
3. Overcoming the British fleet as a prerequisite for invading England.
4. The maintenance of a quality Grand Armee which is potentially diluted by battle losses, spreading it across Europe, and by taking on troops from minor allies.
The brilliance of this game is that it will allow you to employ Napoleonic Grand Tactics, will have to manage the personality and skill sets of the generals in your command, and will have to choose the correct battle plans, given the force composition at that battle.
Good luck and I hope you enjoy the game.