pppoe, wpa-eap in network

Hello
we are using 2 ubnt rocket m5 for access point and mikrotik rb450g. ubnt access points are connected to rb450g.

for radius we are using freeradius.

on access points we are running wpa-eap (ttls) and on rb450g pppoe.

so on client side two servisies are running wpa and pppoe.

Can you tell me overhead of this two protocols?

and is it good or bad idea to use this two protocols in network?

Thank you