when to use base fair tkt vs reservation tkt?

For trains requiring two tickets, I believe I will scan the sucia app on my phone to pass through the initial gate. What do I do with the paper ticket showing my seat reservation?

Do Shinkansen trains have nothing to do with Sucia?

THANK YOU!

What do I do with the paper ticket showing my seat reservation?

In case of limited express trains, you just carry it with you. Most of the time, nobody is going to check it. In some situations, the conductor may ask for it.

In case of shinkansen tickets, you insert them together with the base fare ticket at the same time, but that does not work if you use a Suica. Using Suica on shinkansen involves some special methods. They are explained here:
https://www.japan-guide.com/e/e2359_003.html#shinkansen

I have loaded SmartEx tickets onto IC cards in the past, but because you often go between IC areas it is not like a simple regular commuter train.

360Liz

What kind of tickets do you have? For example, if you bought a paper base fare ticket apart from your paper reservation ticket, you don't tap your Suica to enter the gate. If you tap it, extra fares could be unnecessarily deducted from your Suica.

Tell us from what station to what station you're traveling, and what tickets you bought. I'm sure someone could provide you more details. Or, you can just ask a uniformed personnel at the ticket gate, and the personnel will make sure you don't do anything wrong.