The BMW is the only of the GT3s that's not really coming from a super car, yet it's right up there. It's traits are monumental torque in the mid range, loads of downforce and a rather forgiving aero map, yet it is quite draggy and from 270 kph air really becomes a wall. The power sometimes can come quite explosive and the rear is easily overwhelmed - this can only be muted setup wise and needs to driver to know when to release hell. It can drive both high rake when you have faster corners and low rake /wing when you need traction. Yet, the less downforce you run on the rear, the more pitch sensitive the car becomes as the front always produces a lot of downforce. The setup can cope with that though. Bumps are a bit of an issue, the suspension is sometimes just overwhelmed with the situation no matter what you do. Giving the car more ground clearance can help if the rest of the track layout allows (mainly drag issue). Driving wise you'll benefit being smooth and in a nice flow, the car doesn't like sudden upsets, but it will follow your guidance if you ask politely.

The Track & Setup Approach
Here on Kyalami you get away with lower rake for lots of traction. Downforce does still play a big role apart from all the hairpins. The track has a beautiful flow despite a lot of variety in speeds between corners. Its rather low grip as well and has a smooth surface without many bumps (except laster corner, but that bump is very crucial to getting the car to turn). The kerbs are quite high and only their edge can be used, however the rear end likes to sometimes snap over them if you are too aggressive on throttle. Running focused on a stable car that doesn't use the rear tires too much and rotates steadily, allows for deep braking without losing the rea and overall does not change behavior from situation to situation. You need to trail, coasting much will not work, however a tiny bit of coasting can do wonders to create traction for corner exits. The setup will be good over a stint with only a few laps in the middle that are tricky.

Electronics:
TC1 on 1 or 3 for Q and 3 for the Race to save the rear tires is enough. You can use 4 but it might already be too much. Now you can also watch me change TC in the telemetry data at certain points on the track in order to reduce TC cuts and keep the speed increasing quicker on exits.
ABS on 3-4 seems predictable enough, but if you want some extra lap time try ABS 2.
BB on 52.1-52.7% should be the best compromise between turn in capacity and stability. You can go further back for extra rotation, but try to keep the rear planted into the corners without sliding

Adjustments (you dont actually need any imo)

• if you generally lack with "feeling" for the car, try adding 5 clicks of pressure or so at minimal time loss, but much better communication from the tire
• The spring steps are medium sized, front and rear have the same step size, so adjusting stiffer or softer without much balance change is possible. Try to keep them at the same gap for this setup with the rear always softer than the front to focus on traction but feel free to experiment with different pairings, softer and stiffer. Stiffer will be more predictable but less compliant, softer a bit less responsive, but harder to lose grip. On Kyalami you usually need it softer I feel because of the lower grip of the track
• stiffen the front arb if the nose is too pointy
• move BB forward if too loose into the corners, yet there's also room to go more to the rear still. 
• The car is not sluggish anymore with this setup, but its also difficult to upset the rear, so you can do pretty much whatever with the steering. Don't shy away from turning a little more than expected.
• adjust rear ride height for over/understeer by 1mm steps (higher will always cost traction, try less bump stop range on the rear)

Driving

• you can push into the corner and start trail braking rather late, but need to do it deep
• The car benefits pitching it into the faster corners on the brake a little during initial turn in, this will start the rears rotation and stop it as you go off the brake entirely - hard throttle will keep you going then
• especially out of slow turns feed in the throttle rather than slamming it. Keep it at 80-90% ish until you can open the steering before asking 100%
• aim for late apex in hairpins, try to trail deep, immediate but progressive throttle, little to no coasting in tight corners, aggressive throttle in longer corners.
• yet, SOME coasting can help a lot with stabilizing the car before putting the power down, and the TC won't be as overwhelmed
• long corners will likely not want much coasting in the BMW, you need to load the fronts and then quickly the rears
• power curve is flat, shift at 6900-7000 rpm but do not hit the limiter
• shortshifting out of slow turns might do wonders to driveability (i.e. 2nd gear from most corners)

Lap times:
Q: 15L (Lap 3-4, the first two laps are really not fast. Tire and pressures need time but come alive by lap 3)
R: 108L (for 65m; you can probably use less)