Baggage Question with Airport Limousine Bus

I have a layover in Narita airport and will be using the Limo Bus to Transfer to Haneda International Airport. The Limobus website states you are allowed 2 Bags to check in.

I will be traveling with my 2 check in bags and my rollon carryon bag/stroller that normally fits an overhead bin on a plane. Looking at videos and guides about the Limobus, the their ovehead bin wont fit my carryon. hey are small and can only fit something like a small school backpack.

Is there space inside the bus where we sit I can store my carryon?

Will they allow me to check in my carryon making it a 3rd bag? Is there an extra fee?

I need to plan out early on if I need to change my carryon to a backpack instead which I dont really want to do. Any advice is appreciated.

Have you thought about putting your carry-on below the bus? That will work. There is not enough space for a large carry-on or thick backpack in the overhead compartment. People tend to place backpacks on their lap if they are a little larger. It's been a few years since I've been on a bus so others may fix any mistakes I've made....