Thank you malloc ,The _Banking_Scot, CPH-Flyer, SavvyTravel for the detailed replies and recommendations!

Travelling with a small checked bag that doesn't need shinkansen baggage reservations.

I noticed that my IB281 has been arriving early, sometimes just after 9am, I'm thinking if I might be able to make the 1140 Peach? Need to get from T2 to T1 by Peach's 30min deadline so 1110.
https://www.narita-airport.jp/en/access/shuttlebus/ T2->T1 says about 10min, but I can't find the bus frequency.
If I buy Peach's "Plus" fare, it's 500yen to cancel - latest by an hour before departure so 1040. The fare is good 16990 even with the Plus fare.
The 1320 Jetstar is more relaxing, but maybe a bit too much time in NRT. Jetstar even the highest fare-class is only refund to credit.

I'm thinking buying the Peach/1140 with train as backup....

Thank you!