Here are some guide regarding how to do various things using the pack file manager:

Play as any faction using the tutorial campaign

Open the Startpos.esf and go to COMPRESSSED_DATA/CAMPAIGN_ENV/CAMPAIGN_MODEL/WORLD/faction_array, open the faction_array and select FACTION.

Below the name of the faction it will be True, True, True. Change this to True, True, False to make the faction unplayable.

Repeat so the faction you want to play as is playable and all the ones before it are unplayable.

Put this startpos in the campaigns/tutorial faction.

Start the tutorial campaign and you can now play as this faction.


Increase the amount of money you start with
To increase the amount of money a clan starts with go to COMPRESSSED_DATA/CAMPAIGN_ENV/CAMPAIGN_MODEL/WORLD/faction_array, find the clan, go to faction_economics, and change the 2000 to the amount of money you want this clan to start with. This amount will be increased by 2000 if you play on easy difficulty and 1000 on normal difficulty.

Chance the number of turns per year
To increase the number of turns you need to edit the campaign_calindar in the startpos. Change the 4 to 12 to have 12 turns per year.

Victory conditions
To change the victory conditions open the campaign_preopen_map_info, open victory_condition_options, and open the faction whose victory conditions you want to change.

Victory_condition_block_0 is the victory conditions for Dominion, currently 65 regions by 1600. Change 65 in the Campaign_victory_conditions to change the number of regions needed to win, change 1600 in the Date to change the end year.

Victory_condition_block_1 is for the long campaign (40 regions by 1600).
Victory_condition_block_2 is for the short campaign (20 regions by 1575 or 1580).
Victory_condition_block_3 to Victory_condition_block_5 are for multiplayer.

Make a clan a vassal of another clan
To make Tokugawa Oda's vassal you need to select the startpos, find the World/faction_array, find the Oda and Tokugawa factions (remember their faction numbers), open the Oda faction's diplomacy_manager, find the Tokugawa faction by searching for their faction number, and change the first neutral to patron.

Next open the Tokugawa faction's diplomacy_manager, find the Oda faction by searching for their faction number, and change the first neutral to protectorate.

As a clan can only be the vassal of one clan you need to change Imagawa's diplomacy so Tokugawa is no longer their vassal (change patron to neutral).

thank you , but can you write how to change clans relation , so Tokugawa not hostile with Oda ? so if someone play Oda they can have trade and gain benefit from Tokugawa

You just need to change the relationships from "hostile" to "neutral" in the diplomacy_manager. The "Make a clan a vassal of another clan" part explains how to do this.

you don't understand me . i try to change diplomacy_manager table like this , but Motoyama still unfriendly with Chosokabe , and they refuse to trade
System
True
0
patron(protectorate)
0
20
0
0
0
0
10
0
False
0
patron(protectorate)
False
True
45
0
0
True
System
True

Try using this version it should make Motoyama like Chosokabe more and have them start with a trade argeement. Remember you need to edit the diplomacy for both the Chosokabe and Motoyama factions.

System
True
0
patron(protectorate)
0
20
0
0
0
0
10
0
False
0
patron(protectorate)
True
True
90
0
0
True
System
True

i change like you said but Motoyama still unfriendly , and my clan income don't have trade gold from Motoyama , but their diplomacy show that already trade

i downloaded and opened old mod Oda tokugawa allies by Gallus , i saw what he change is like that
id clan
0
patron(protectorate)
0
20
0
42 <- and this
0
0
0
0
0
10
0
System.Byte[64] <- this is different
0
patron(protectorate)
False
True
115 <- and this
0
0
0
0
True
System.Byte[0]
True

can we change to 24 turn/year like Fall of sam ?

Yes you can by editing the startpos.esf. You just need to enter 24 instead of 12.

Where do I find the line to edit the starting capital of the Ikko Ikki? I really want to start with the port in Izumi. I'm used to modding with rpfm and EditSF.

@Kapitan Wolfgang
What you want to do is very complex. It would be easier to use the official modding tool to make a new startpos, rather than trying to edit it manually.