Some questions

[Blxz]

Client rulers can be interesting but look out for the area of recruitment. Building level 4 governments in your core cities will restrict your troops greatly. Better for the outskirts of an empire or for towns that have very high revolt risk issues.

[Titus Marcellus Scato]

Client rulers can be interesting but look out for the area of recruitment. Building level 4 governments in your core cities will restrict your troops greatly. Better for the outskirts of an empire or for towns that have very high revolt risk issues.

Indeed, best use of Type IV is in cities that are far away from your homeland and not of your faction's culture, so you can't recruit a lot of factional troops anyway. In such cases, the regional units available are usually better than your factional ones.