Oxiracetam is just better for something like that because it's very much like a stimulant. I haven't use modafinil either but adrafinil is basically same thing just need to consume more to get same effect. I like adrafinil but only take it on an as-needed basis. Taking adrafinil with oxiracetam will have a more noticeable effect and definitely help with giving a presentation IMO. I don't play around with all the nootropic mix supplements, for me I just use a racetam/noopept with adrafinil and a choline source like alpha gpc.
If I were you, I would take alpha gpc, oxiracetam and adrafinil before the presentation. It'll give you the energy, confidence and mental sharpness needed to put on a great presentation.