What about going to gt6 item pipe or hopper to pipe or so then try to insert sifter (shorter distance) else to centrifuge (further distance)?
Or could put export on both and disable the centrifuge one via redstone until the sifter stays empty for a bit then pulse the centrifuge one on occasion in that case?
(I’d go for pipe one first if that works for you?)
Or use a Logistics Core!