In the various sea trips I have managed to avoid races altogether by going at slack tide or well out to sea.
A trick played by races is that a very calm sea can give you a false sense of security and lead you into the race, the tide accelerating; then you are committed.
These kayaks had a go through the St Catherine's race, where you can see it goes from smooth calm with a slight swell to a challenge in about 45 seconds.
They were experienced and knew what to do; after another two minutes the sea calms down comparatively. It would have been what a sailor calls a 'hairy moment' talked about in the pub afterwards.
A race often forms by headlands where the moving water is compressed, speeding up and causing rougher conditions.
If the turbulent water also encounters waves going in the opposite direction, the water is more likely to break, with short sharp waves collapsing.
Also, if two streams converge then this results in rough water as in the illustration of tides off the Hurst Point, entering the Solent. I avoided this by keeping close to the Isle of Wight.
However, the same things happens off the Needles and I had to go through the rough patch on that occasion, but with such a calm sea and the tides almost slack it was no problem until mainly through.
There is a great book called 'Coastal Turmoil' that explains it all, the above illustration taken from this book.