It's not a dumb question. It's smart to realize that you need to consider travel details that you haven't had to deal with before.
I'm wondering how long and what kind of a trip you're taking. I'm also wondering the following...
Exactly how big are those "large" bags? What are the measurements in inches or centimeters including wheels and handles? How much do the large bags weigh empty in pounds or kilos? What is the volume in cubic inches or liters?
And how big are the "average" carry-ons with all the same details for each?
Are you planning to have anything else, like maybe a purse or camera bag or messenger bag or bag of food and drinks, to get on and off the train with everything else?
As a solo traveler who has to be able to handle her luggage herself, large to me is anything over the standard 22"x14"x9" carry-on. My heaviest bag is that size and weighs 5.5 pounds empty. I haven't used it since 2018 due to that weight.
My best bags are all lighter at 4.5 pounds empty. My favored ones, used in 2019 and this year are "international" sized.
The one I used in 2019 for a trip of 5 weeks is expandable, 20.25"x14"x8-9.25" with a volume of 36-39L. I've never used it expanded. In addition I used a 16L 2.2 oz cross-body bag for my personal item.
The other I used this year, also for a 5-week trip, is not expandable, 19.5"x16"x8" with a volume of 38L. In addition I used a 25L, 11 oz backpack for my personal item. The only time it was full was when I put my zip-up fleece in it.
I mention this because of all the advice others have given about the difficulty of getting on and off trains with too much luggage to handle efficiently. Even at 76 years old, I was able to get on and off the variety of public transportation modes I used this year better than ever before.
Personally, I pack for a week, no matter how long the trip. I prefer to do my own laundry at a self-serve laundromat or have it done for me. Both those options have led to enjoyable encounters with local people and other travelers. I'm not a fan of sink washing in my room, but I'll do that if I have to.
For me, the size or type of bag is dependent on the clothes for the trip. Over the years my basic formula has been 3 pairs of pants, 8 tops of various kinds and 2 pairs of shoes. All those pieces coordinate with an "inspiration" scarf so that I can put any of them together.
I wear my heaviest shoes in transit, along with one of the pairs of pants, the scarf and 1-2 of the tops (depending on the weather or anticipating a cold plane), so I don’t actually need to pack all those garments. My fully packed carry-on weighed 20 pounds this year, my self-imposed limit.
Having 2 people to schlep the luggage may sound like a good reason to take a lot of stuff and big bags, but it probably isn't if you double+ the amount of stuff you're taking.