Found a new kingdom question

[Raspustein]

So i have googled around to try to find a answer and im now probably more confsed then before.
I have taken the south of england, and have 3 de jure dutchies and now have the option to found a new kingdom. my question at this point is would it be best to do so now, or wait till i take the rest of the island and then do it, what are the benefits of either choice, and do new counties and de jure dutchies that come into my realm after get the same protection as the ones i currently have?

[Storm]

The found a kingdom option automatically makes all duchies you own de jure territory for the new kingdom; even to the point of transferring them from their empire to your primary duchy's de jure empire. After you form it, assimilating new duchies will take the same amount of time as standard based on your gamerules (default 100 years).

Waiting to take the rest of the island has the advantage of making it, obviously enough, a single kingdom title. The only real reasons to form a custom kingdom immediately are worries about de jure claims being pressed, or that you are running out of vassal and demesne limit.

[quarre]

Or if you want titular kingdom title + new one with cool shield. Like, i always do this thing if play as norse, to save Ugra shield with deer xD

[Azunai]

it's kinda hard to take the whole island without a kingdom title. since you're a duke, you can only have count and baron tier vassals, so you'll probably run out of vassal limit when you can't hand out duchy titles.

if you control more than half of the dejure territory of an existing kingdom, you can also create that kingdom title. which gives you de jure CB against everyone who belongs to that title and isn't de facto part of your realm yet.

IIRC the kingdom of england has 29 (?) counties, so if you have 15 counties that belong to england, you can also create that title and get de-jure CB for the rest. plus there's a high chance for independent counts in your de jure territory to peacefully submit to your rule if they like you enough (get their opinion to +30 or so and offer vassalization)

also, your vassals give you an opinion malus if you have more than 2 duchies and you'd have to hold something like 10 or so if you want to control the whole island before creating a custom kingdom

[quarre]

The kingdom of Wales is 8 counties, so its easy to make and you can hold all of it by one character, and keeping its as single duchy without splitting in 3. Or cut it for 6 counties and pass on Cornwall for guarantee.
Strong base with no vassals higher than barons plus you can have elective monarchy where's you one and only elector :)
By me, Wales is a good point to start unifying of Britannia since its between England and Ireland, so you can expand in both sides.

[Random]

when I play england I always make a titular kingdom title in the south to split the english kingdom's dejure in half. if you don't england as a vassal is too powerful compared to the other neighbouring kingdoms, so weakening it preemptively before you become empire of britania will help lower future bordergore.

When you make a titular title all held titles will be transfered under the new title AS LONG AS THE NORMAL DEJURE TITLE DOESNT EXIST. So if mercia merges with northumbria and creates the kingdom of england in the north while you hold 5 duchies in the south, when you make the titular title it will NOT transfer your duchies dejure to it, they will remain under england and your kingdom will have no power except for allowing you access to kingdom level benefits, but when you land vassals they will not be controllable by your laws as they are outside of your dejure.