Aventurian Tech-Level, globally, is a straight 3 - middle ages. While some technologs maybe higher, the goal and mostly accepted reference is to the middle ages. This does not mean that all states share the same tech level. In general, the Horasian state is a TL 4 society, naturally (in proper Aventuria) without black poweder weapons, but their non-gun-powder equivalents. Thorwal is a straight TL 2 society. Some of the southern islands are TL 0 or TL 1, naturally.

In general, when going to the countryside, the tech level will drop by at least one, though material of the higher TL will still be available. So, when in Thorwal (TL2) going to outskirt settlements, you may be in a TL 1 society with TL 2 weapons, but the infrastructure will in general mostly support TL 1. When going from Kuslik (Horasian, TL4) to some outskirt settlement, you will find a TL 3 society, though people will have TL 4 quipment.

On the other side, given enough time and money, you will even find TL 4 weapons in Festum (Bornland, TL 3) and even TL 4 medical care by someone who did study in Kuslik.

Please note that the Gurps TL related rules, especially regaring starting money and medical abilities, do in fact make the TL differences a lot harder than they were in original TDE. This is considered to be beneficial, as it puts more emphasis on cultural differences.

For characters, please apply the High TL / Low TL Advantage/Disadvantage as appropriate. It is adviced to always assume that the standard TL is 3, as aventurian heroes, mostly, will travel through all of Aventuria.