Shinkansen Booking for Group of 7

Hi everyone!

I have been getting overwhelmed when researching the best way to book a shinkansen, especially as i am travelling with a group of 7 and am looking for a straightforward response/advice! We are all travelling with luggage that would require the oversized baggage seats/reservation, however, I understand that the maximum i can book in a booking is 5. Now, from what i have seen, there are only 5 of these seats on a whole shinkansen? Or am I mistaken with this and there are multiple carts with the oversize baggage seats.

I also wanted to ask about the best way to reserve our shinkansen tickets (we are travelling from Osaka to Kyoto, and Kyoto to Tokyo). Is it best for our group to reserve in advance (through klook or smartex app (which one is better?)) OR buy these tickets at the station (i would prefer this option).

If there is an issue about number of oversized luggage seats in a shinkansen, we are also willing to luggage transfer between cities, but there is concern of if they would arrive same day instead of next day – which is why we would prefer to just take our luggage on the shinkansen !

I apologise if this is lengthy or doesn't make sense but all of this research has been overwhelming with everyone saying different things!

by ButterflyUnusual9213