Alright. My tweaks for anyone who is interested. Firstly the player file. This is found in your userdata folder. In my case it would be: UserData\Alex Coady and be the file Alex Coady .PLR file. FEEDBACK APPRECIATED!
Make a backup of this file and move the back up outside of the RF folder or clashes may happen.
Find the following lines and change to the following.
Bold is my explanation of why.
AI Power Calibration="7" // Adjustments with AI strength (0=none, or add the following: 1=power, 2=gearing, 4=fuel)
This is recommended by many modders, I just stick it in.
AI Fuel Mult="0.99000" // Additional fuel multiplier for AIs because of their driving style
Same as above.
AI Tire Model="1.00000" // 0.0 = use AI peak slip, 1.0 = use player's dynamic slip, or a blend between the two (can be overrode in TBC with AITireModel)
AI use the players tire physics.
AI Brake_Power Usage="1.28000" // Fraction of theoretical brake power that AI attempt to use (can be overrode in HDV)
Power of the AI brakes. The higher the harder the AI brake and the quicker there deceleration is. 1.28 may seem a high number the reason why will become very clear.
AI Brake_Grip Usage="0.92500" // Fraction of theoretical brake grip that AI attempt to use (can be overrode in HDV)
The higher this is, the better the AI thinks it can brake on the road. If this is too high in partnership with the "AI_Brake Power Usage" line then AI cars will think they have tons of braking grip and run straight off and crash.
AI Corner_Grip Usage="0.98000" // Fraction of theoretical cornering grip that AI attempt to use (can be overrode in HDV)
Also works in relation to the above, I would not raise it above this.
AI Max Load="4500.00000" // Maximum total load to set up theoretical performance tables (can be overrode in HDV)
A big one. The lower the Max Load, the harder AIs corner, accelerate. With the wrong settings AI will just understeer and speed off the road. They also will attempt more interesting overtakes. If you are not happy, 10000 is better suited for say, endurance races.
AI to AI Collision Rate="40" // Detection rate per second (1-40) for AI-to-AI collisions
More accurate collision physics. If you have CPU problems, change to 20.
Auto Line Smooth="3" // 1 = fastest line, 2 = inside/outside, 3 = fastest and inside/outside
AI don't just use one racing line.
AI Limiter="0.00000" // Range: 0.0 (no limiting) - 1.0 (limiting used to make racing closer but also make more driver differences on flat-out tracks)
0.0 means the AI will drive there very hardest whole time, which means they do spread out a little more. If you don't like this, I do not recommend going above 0.250000
AI Mistakes="2.00000" // a range of (intentional) AI mistakes from 0.0 (none) to 1.0 (sometimes). Anything above 1.0 multiplies the frequency
The AI Limiter means in theory they should drive perfect races. This line however means they will make mistakes and crash more. 1.25 is lowest I would reduce this to.
Vehicle Removal="120.00000" // Seconds until stationary vehicle is removed from track
Debris Removal="120.00000" // Seconds until stationary debris is removed from track
Parts Duration="120.00000" // Seconds after parts break off before disappearing
Self explanatory. If a car is retired and stopped, it will be moved off of the track a full 2 minutes (120 seconds) after it stopped moving. A car dissapearing off track after 5 seconds isn't realistic after all.
.HDV tweaks (optional)
Vehicle physics - often found in RGameData\Vehicles and then mods and cars folder.
AIMinPassesPerTick=8
2 is default. This is to do with how much CPU AI uses for calculating cornering physics. The more you use, the higher your CPU rate will be but also AI cars will be faster and more stable and accurate. 8 is what I can get away with on the Super Touring mod due to it being very fps friendly, but even a change to 3 or 4 can help. DO NOT set to 1, or AI physics can go very wonky.
AITorqueStab=(0.65, 0.65, 0.75) // torque adjustment to keep AI stable
Stability of a car under Acceleration, Deceleration and Cornering. May vary from 1.0 to 0.5 depending on the mod. Too low and AI wreck and flip and crash like paper.
Damage files i'll work on later
, getting passed by a car sliding across the grass on the kerbing is a shocker 
