Since you have 3 loggruops you don't need to add any more.(well you can always ) but i don't think that's necessary.
Destination of arch files.
try to reduce the time of redo log switching by increasing the size of redo logfiles, on a default db creation it's 1mb each ,make it 10mb each or so.
you don't need to create any aditional arc processes as the lgwr automatically starts one if necesary but you can do it if you want to.