Yet another public holiday question

I will be in Japan this September and see that as well as Monday the 21st being Respect for the Aged Day & the 23rd being the Autumnal Equinox, Tuesday the 22nd is also designated a national holiday. I was wondering how much this would affect the trains (mainly Shinkansen) on those days and on the Saturday & Sunday preceeding. Thank you in advance.

Expect more crowds than usual and try to reserve in advance if you can. That is considered "Silver Week", and while it doesn't get the crowds Golden Week does, people are still going to take that opportunity to travel. If you can, consider instead traveling on Sunday/Monday/Tuesday instead of Friday/Saturday/Wednesday as those will be the heaviest travel days.

Thanks for that. Not the best time to transit Tokyo with large luggage then. I will have to rethink my plans.