Wait you said you wanted good novels why did you mention something like dragon ball and fairy tail. DB is inconsistent as hell and the other has an extreme case of power of friendship power ups lol.
It depends on what era it is. If you place it in the original db setting before the saiyans you could write a very amusing story with much clearer boundaries on power. But yeah any fanfiction of the latter parts will feel off since the author is free and clear to do any buttpull plot development they want and still have it fit the boundaries. Also inconsistencies don't necessarily ruin a story, someone with a yuyu hakusho pic/name should acknowledge this. It's possible to more than make up for the shortcomings if the quality is good enough.
https://m.fanfiction.net/communities/anime/Dragon-Ball-Z/ https://m.fanfiction.net/communities/anime/Fairy-Tail/