The 23 and 27 have a lot of BS written about them. They are pretty straight forward if used as intended - low level strike, so straight line no turning and burning.
The main two issues with them are firstly the engine - which is not super reliable at the best of times, but when it experiences long or latitudinal stress has a nasty habit of distortion and self immolation. we are not talking serious g here. Secondly lateral stability, it snakes like a bitch hence the lower stabiliser which extends with gear up. This gets a fair bit of abuse so rarely stays straight for long, compounding snaking and trim requires continual attention. The indian air force had a pretty good serviceability rate around 70% most weeks. Not sure on the numbers for Bulgaria, GDR etc.
If your flying at sub 100 feet and need to fly at warp factor 1 plus with a smooth ride that wouldn't trouble your haemorrhoids it was a great option. Just don't bank, yank and expect a good outcome.
https://www.instagram.com/darkroomeagle/
anyway, some great shots of the ejection sequence here - looks like late life upgrade seats fitted too