Personally I can vouch ha_ha_ha. I'm staying at Damansara Damai, and bought a house at Gamuda Garden (2024 completion). I used to travel a lot to Saujana Utama/BSC. Sometime from Shah Alam, sometime from Damansara Damai. I can say that using old road is way better than using NKVE exit Rawang(S) due to the bottleneck. You should explore more old road at Paya Jaras/Kuang using small road. You can reach BSC with smooth traffic but not that fast.

Usually if there is a heavy traffic due to accident at Old Road, I will turn right @ Paya Jaras - Kuang Road, until you see petronas/caltex, there will be a 4 junction, make a left and straight until you found Kundang Tol @ Latar, from there you can enter highway again and exit to BSC. OR if you're from NKVE, you can exit Sungai Buloh (S) then take the road to Hospital Sungai Buloh, right before Hospital Sungai Buloh there u can take left and go to Kuang (lalu jalan Daikin)

I also afraid once my house at Gamuda completed, there will be a massive jam at the Later-NKVE toll. Right now it is super damn busy... but only for TNG toll. Gamuda plan to make business center left & right at the toll with Luge sports game. Hopefully the developer can contribute to improve the traffic...