I think larps are slightly different I would say https://loxwoodjoust.co.uk/immersive-festival/ where the visitors see the reenactors, and while some cosplay, the renenactment is a performance by a cast.
Where as LARP (e.g. Empire) is all the “visitors” are in the cast
I LARP with medieval theme. Most speak English…most don’t verily and ye (which is wrong as y is th anyway,). Some out in Scots accents for Celtic twist and some dinput on French accent for the rennaisance France flaire. But most just talk normally.