1-
The code has greater map visibility.
The code will see the units of the player from at least 5 provinces afar, whereas the fog will cover the player's vision down to 1 province adjacent.
2-
The code has no naval attrition, almost zero land attrition, and additional manpower.
No need to explain, but as an example, if the player moves a 10k force by sea from Amsterdam to Cape without monthly stops at a port, that force will reach the destination as only a 1k force. In contrast, the code will casually send 100k troops from London to Aleut without any loss. The player-castile will have a hard time to accumulate 25k manpower while code-france will reach 100k manpower in no time; conversely, code-castile can accumulate 40k manpower without any idea sets, whereas the initial manpower-cap for player-castile is hardly around 27k. About 1% of the maximum manpower determines the default rate of manpower recovery, therefore a 100k cap means roughly 1k manpower per month, effectively provides infinite manpower, and the code has higher manpower cap-level than the player.
Even with these bonuses, the code will manage to exhaust all its manpower, and yet will be able to field its full force. When a player is left with nought manpower, and if there is no other source to recover
(multiple wars, no merc available, no professionality to slacken standards, no mysticism for muslim-tags, no special units left, etc.), it is practically game over for the player, especially during the initial phase.
3-
The code will always lucky-strike.
And the player will be rolling 1 after another 1 for any dice related action; from siege rolls to hiring generals, from events to battle phase rolls. Not to mention the average of the ruler skills, traits, life-expectancy etc. the player can get against the turbo-rulers of the code. This point is not verifiable, and heavily contaminated with confirmation bias, but the end result will be seen always as the player rivaled by the code-greatbritain, with a 6-5-6 even for a regency, and the player is the holland-tag of 6-provinces, recently gained independence, with a first ruler of 0-1-2.
4-
The code has greater range for choosing rivals.
This is one of the bigger issues that makes the power distribution asymmetric, and it is only a concern for the beginning, because beyond the initial phase (1444-1500), there will be less tags left and most probably the player will be undefeatable in any case.
Still: This is the reason for the player-brittany of this run started with a rivalry with the code-portugal. As such, the code-portugal will try to ally with the enemies of the player-brittany, try to proclaim guarantee any weaker tag the player has a border, send gifts and give subsidies to any war opponent of the player, send privateers to its ports, and worst of all, it will try to out-colonise the player if both are colonisers, which is the case in this example.
It is therefore when the player sends colonists to northern America colonial regions, the rival colonisers will send there too if not before (they will, as it is the portugal-tag). Under no circumstances there can be any, and any, benefit the portugal-tag can get from a colony in northern colonial regions: The trade nodes of the region do not flow into the Sevilla node, and by sending a colonist there it foregoes other regions to colonise, etc. But the code-portugal will colonise there only to disrupt the colonial route of the rival player-brittany without caring about this opportunity cost, and it will still finish up all those colonies before the player and then fully colonise Guinea area in Subsahara
(portugal-tag specific colonising bonuses, plus lucky nation bonus, plus code bonus).
And in contrast, when the player is the portugal-tag, then it will be seen that the code-brittany is not available in the list of eligible rivals to choose from at the beginning - only morocco-, tunis-, castile-, aragon-, tlemcen-, and granada-tags are available to the player-portugal for a rivalry.
5-
The code diplomat.
This is the greatest advantage of the code: The code diplomat.
A duchy-level tag starts with 2 diplomats, and kingdoms and empires have 3 by default. The papal-tag has 4 diplomats due to papacy-curia mechanics, the ashikaga-tag has 4 due to shogunate, and some tags start with extra diplomat by their traditions.
Additional diplomats can be gained only through idea sets (diplo, aristo, espio, and policies), reforms of
mandate of heaven and
hre, parliament actions for republics,
tengri syncretic with
theravada, unlocking national ideas of some other tags, etc.
So, as an example: The brittany-tag starts as a duchy, it has only 2 diplomats at the beginning. The portugal-tag starts as a kingdom, it has only 3 diplomats.
But the britanny-tag is the player, whereas the portugal-tag is under the code control. The portugal-tag starts with 4 diplomats. In fact, all code tags start with +1 additonal diplomat.
And that is the code diplomat reserved specifically against the player, especially when a rival and/or with
hostile attitude.
Therefore the code finishes up initial alliance phase before the first month of the run ends, and at the same time within the next 12 months is able to fabricate a claim on the player-tag.
Therefore the code rivals will bombard the player with slander merchants, sow discontent (especially if none of the humanist or religious sets is chosen), sabotage reputation (especially after annexing a vassal), continuously.
Therefore the code will always have 100% spy network on the player-rival while improving relations with 2-3 other tags, thus it will maintain +20% siege ability against the player.
Therefore the code-france, the code-muscovy, the code-timurs can annex their starting vassals much quicker than a player can ever do.