>>536348505
There are cases where that kind of shape can be 'worth' keeping as the outer tile (4) can be seen as a floating tile that can turn the shape into a penchan and kanchan/ryanman by drawing a 5 or 6. It might also be worth keeping if you really need a nobetan for some reason. But generally speaking if the above is a 'better' option than almost anything else your hand, your hand is already in dire shape. Obvious stuff like sanshouku and dora acceptance excluded (but remember that a tanyao is worth as much as a dora, so if the 1 is dora it still may be worth cutting it for a 34 ryanman tanyao over a 13 dora kanchan). I guess for the 124 shape, if your hand is already really good you could try a sotogawa trap discarding the 4 but sotogawa traps are kinda trash. Penchans have terrible acceptance and because of that tend to become terrible tenpais, they are rightfully maligned.
Chanta is probably the worst yaku in the game. Chase it if you can force an off wind dora pair/ankou and your hand suits it, but those situations are very rare. Chase it if you can squeeze an extra han out of a yakuhai without dramatically slowing down your hand. But generally speaking, don't chase chanta, it's trash. a single dora or aka is worth as much as an entire chanta.