Some findings till now
I must agree, the bloom is too overexposed when just installing it. But setting "BloomPowerDay" to less than 10 makes it reasonable. Setting "BloomFadeTime" to a lower value makes it so when you go underneath something and you get out again the bloom is very big for a short time. This might be realistic, but I have never really given it a thought when driving out of a tunnel IRL.
Setting BloomAllowOversaturation to 0 distributes it much more evenly. So parts on the track/car that are already shiney don't light up like a christmas tree.
Maybe setting the carshine value in the LFS configuration file even lower, gives more room to play with this ini file. I like the skies etc, but when having a yellow car it seems to be painted with some fluorescent paint.