I tried *121#, and I saw a smart offer option. If this is the smart plan you are referring to, it could work in completely running a pruned node if you spend up to #90k worth of data. Meanwhile it is still not better compared to the Hynetflex plan
You can go for the normal data subscription if you do not want the Hynetflex which are for the routers. This is it:
It is the same price with Hynetflex if it is a year subscription. Before MTN increased it, normal data for 1 terabyte was ₦100,000 while it was ₦150,000 for 1.5 terabyte if in is Hynetflex. But after the increase, if you make the calculation, you will still see that the yearly subscription for both are still the same.
Also I have seen the yearly subscription to be the cheapest.