I will like to summon entities without having summoning sickness effects, is there anyway to disable it? since i can't find an option to disable summoning sickness effects even in config files.

No, it shouldn't be disabled. It prevents certain combinations of spells from locking your server out with hundreds of thousands of entities.

oh, so disabling summoning sickness may cause certain issues, because i just want to try summoning more than 20+ entities at once, maybe adding a config options to disable summoning sickness, so i can disable it at my own choice.