Uses Vodafone 4G network (5G is only for their largest monthly plan). Check the coverage in the areas you frequent before buying.
Apparently Optus and Vodafone will be sharing their networks in regional areas some time this year to better compete with Telstra. Do your own research to figure out who owns the mobile towers in your area if you live outside of major cities. A good value plan is worth nothing without adequate coverage.
The sale for the 500GB plan ends on the 2nd of February. The 300GB one lasts until the 16th.
Once purchased, the voucher codes themselves will expire at the end of February for 500GB and end of March for 300GB.
Vouchers can be used on existing Kogan Mobile services, but will not "stack". It will override the existing plan and start the new one immediately from date of code redemption.
This with 5G access is quite comparable. https://www.ozbargain.com.au/node/888208 it’s now $169 Plus 15% cashback from Topcashback which brings it down to $143.65/year. 250GB vs 300GB though.