Not much. The game tries to keep the total player count close to the starting count, with a small amount of fluctuation year to year.

Yes. A lot more players are produced in the first year than later on, but it stays consistent after the first 2-3 years.

Short answer, no. The proportion & potential of newgens coming from each country stays roughly the same.

Long answer, it’s possible for it to change due to the dynamic youth rating, but this is a very small effect that’s unlikely to be noticed unless you’re simulating decades into the future. There is also a large amount of chance involved in youth intakes with the possibility of golden generations or talented players appearing in unlikely places.

The results on the scouting map are from a very large set of players generated from different game setups. Some nations turned out better or worse than I expected, but this can vary between saves, especially if you use mods or custom data packs. The top 10-15 nations were consistently the same across all vanilla game setups, but below this it can change from intake to intake, with many countries having some chance of producing talented players.

I don’t recommend loading a lot of playable leagues unless you don’t care about game performance.

Using the game setup options to add players to every continent greatly increases the number and variety of youth production and I’d recommend doing this unless you need to run a very small database for performance reasons. The different options allow you to customise exactly how many players you want to load.

On slower PCs, you could load players to specific nations only to keep the size down. You can use the scouting map to identify appropriate nations based on the teams you want to manage (e.g. a large database of English players would be unnecessary if you only intend to play in South America, but Mexico would be worthwhile).

I can’t tell you exactly as it may run much slower or faster than it does on my PC. My preference based on my tests is for a total player count of 150-200k with 5-10 playable leagues.

No.

Yes, a lot more.

Potentially yes, but it varies a lot depending on exact setup options. Under certain circumstances playable leagues will create newgens at the start in addition to the database of real players. These tend to be low quality, but affect the number of players in future youth intakes. I wasn’t able to identify the cause of this in my testing.

Yes, but it really depends on your PC and your preferences to what is fast enough. Loading players without loading playable leagues is much faster than loading playable leagues. Higher end PCs can easily run with player counts over the limit recommended by the game and maintain good performance.

Yes, from my testing it will slow down for the first 10 years of a save, after that it doesn’t change much. It ends up with a season taking about twice as long as your first season. Any game setup will slow down, though this will be more or less noticeable depending on your PC and starting speed.