I am relocating to Beijing from Shanghai so I have more than one suitcase.

As i know, although the policy says 20kg per person, the rail system are not as strict as flight. Usually as long as your luggage do not looks too marge, no one would weight it. So you can take your 2 suitcases with you directly.

Use a delivery service. I used to commute by speed train to Beijing for business. Prefer it over flying because I wasn't that much more time when you take into account airport security etc and I'm connected the whole trip so I can work.

My assistant would send my luggage ahead via one of the shipping companies so I just needed to carry my laptop. It cost me roughly 30rmb 3 years ago. The bag was a folded laundry/suit bag. Biggest that a large backpack, but smaller than a large suitcase.

Good luck with the move!