One thing about storing terrain boards under the table is that they need to be protected from stray feet and knees, either with a door or by being significantly smaller than the board above. Under a 4'x 8' table I would not store boards more than 2' wide without a cabinet door for example.
Table height is also a big issue and there is no right answer. I see most between 32" and 48", it just depends on your own height and play style. The big thing is experiment - try a temporary table at different heights and see how it feels.