The highlight warning blinkies are a very reliable determinant of raw clipping with Fuji cameras - beyond easy to ETTR accurately. The luminance histogram can be workable as well, but as it can easily fail to register small areas of potential overexposure, I find it far less useful than the blinkies. Besides accurately predicting overexposure, the blinkies show precisely where any clipping will occur, making it easy the distinguish between specular highlights (which can be allowed to clip), and important highlight detail you want to keep. I don’t use a histogram at all. I don’t know about how most other current cameras fare in this regard, but I believe the Sony zebras are useable for this purpose as well.