You’re comparing technology of the 1980s to today’s technology. Nuclear power research has come a long way since then.

Part of the reason NPPs (as in, conventional PWRs, as we use in the west) had to be so big is the giant containment structure to keep pressurised water inside the reactor. Molten salt does not need to be pressurised and is much more efficient because it runs at much higher temperatures than water does. So these two technologies combined definitely have the ability to reduce the size of NPPs.