I think it would be easier to start with Talent files, It would be possible to adjust certain aspects of the car, like the engine's power, the tires' grip, and the brakes' strength. However, making these changes can be quite complex.
for example
In the tire file, there is a table of numbers called the "tire slip curve". This chart shows how the tire behaves when it slips at different speeds and angles. This is important to understand, but not what we want to change.
Instead, we want to focus on the sections of the tire file that define the different types of tires, such as soft, medium, and hard. At the beginning of each of these sections, there is a line that says "Drylatlong" followed by two numbers in parentheses.
These numbers represent the tire's grip on a dry track surface. By adjusting these numbers, we can increase or decrease the amount of grip that the tire provides. This, in turn, affects how the car behaves on the track. For example, increasing the grip value will make the car easier to handle, while decreasing it will make the car more difficult to control.
The first number represents the lateral grip coefficient of the tire, which is the tire's ability to provide grip during cornering or turning. This number is typically higher than the longitudinal grip coefficient, as cornering requires more lateral force.
The second number represents the longitudinal grip coefficient of the tire, which is the tire's ability to provide grip during acceleration or braking. This number is typically lower than the lateral grip coefficient, as the tire needs to transfer weight to the front or back of the car during acceleration and braking.
This will not specifically slow the Ai down in the corners but rather change the way the Ai behaves during the corner as it adjusts speed for the available grip level. and adjusting these numbers by very small amounts will make a noticeable difference. I normally adjust by 0.1 and test.
Next would be the brake power adjustment.
In the RCD file, the term BrakePressureSetting refers to the pressure setting of the car's brake system. The number that follows represents the maximum amount of pressure that can be applied to the brakes.
A higher number for the BrakePressureSetting means that the brakes can handle more pressure and, therefore, can provide more stopping power. However, too much pressure can cause the brakes to lock up and the wheels to stop rotating, which can make the car spin out of control. So, the BrakePressureSetting needs to be carefully adjusted to find the optimal balance between stopping power and control. It is important to note that the Ai will brake earlier if there is less power available. Again small changes.
These are just a couple of things you could possibly change. There are many more. Maybe jgf will have a more simple approach, I tend to overcomplicate things.