YouTube takes - as long as YouTube takes. There is nothing odd or special about LumaFusion video exports to make them slower than anything else - but - check/compare bitrates etc of your videos as this will affect YouTube's encoding
How often can you expect updates? They are released 'when they are ready/reliable' - it's only a small team of developers
Audio - no there shouldn't be any advantage from an iPad Pro - but gain check your output bitrates - they can be changed
Community - you asked some questions - I replied
- although I am 'The Grand Master'
- I don't know everything but someone will usually come up with an answer
Hope that helps