Yes. A weaker B debuff (like Mordred's 10% Outrage) will just miss against a stronger B debuff (like Dartagnan's 20% Sniper Shot). Sniper Shot will overwrite Outrage, but this is currently bugged, so make sure to apply Sniper Shot first.No... well, SSR Amon has -25% which is currently outmatched. But -50% is the cap (for Def, no cap on Atk debuffs until valentine).One way is the encyclopedia in Sanahtlig's toolbox gives you a quick peek on all the skills, including upcoming ones.