That's the
policy. The reality is more complicated, inconsistent, and unclear.
Checked baggage service in my experience is rare, and actually figuring out whether it is available is hard. It appears it isn't available on any NYP-ALB service, so unless you're starting from Albany, checked luggage would not work for this trip. It used to be available at some (maybe 10% or fewer) stations on the Pacific Surfliner route, but is 'suspended', so it appears it is now only available on very long distance routes. So if you have a connection, you likely won't be able to check baggage. If your connecting short route does offer checked baggage, you'll need to make sure your connection is at least two hours.
Carry-on items can be larger than on a plane and 50lbs, but the trains are poorly fitted to accommodate these, and you'll need to handle the luggage yourself. On the NYP-ALB trains in my experience, for example,
there is one luggage rack for large luggage, able to fit perhaps eight pieces at most, for an entire car; since it can be converted to a bike rack, if a single passenger checks a bike, all that storage goes away. There's sometimes space on the floor toward the ends of the car, and sometimes not, and using it is unclear. The remaining option is overhead, so you'll need to be comfortable lifting those 50 pound items above your head while surrounded by impatient people. Just to get them on the train, you'll also need to carry them up rather difficult steps, while surrounded by impatient people. You also need to keep in mind, while placing your luggage, that
different doors may be in use at different stations, so if your luggage happens to be in the wrong direction for the the flow of exiting passengers, you'll have a challenge getting to it at a short station stop.