Is it ok to buy Shinkasen/Shinano train tickets on the day for these routes and days?

Hi all, I'm planning to take the following transports during my imminent trip to Japan:

• Shinkasen from Aomori to Hakodate on 14/08
• Shinkasen from Hakodate to Sapporo on 15/08
• Shinano Limited Express from Matsumoto to Nagoya and Shinkasen from Nagoya to Kyoto on 20/08.
• Shinkasen from Kyoto to Tokyo on 21/08.

I am assuming that I can just purchase any of these tickets on the day from a vending machine at the train station (no reservation, as I travel just with a trolley). Is my assumption correct, or the increased influx of turists (I visited Japan last time in 2018) has made it necessary to purchase tickets in advance? Also, should I worry about any festivity or particular event on those dates/location that could spoil my plans? Thank you very much.