My question is what affects staking weight more, the number of blocks or their size? Is there some formula for this?
Good question! From what I have seen total number of Beans matters most but number of blocks and block size are very important. Its kind of like a lottery system. If you have one big block then you only have one ticket, one chance to win, but if you have many blocks then you have many more chances to win. With 190k Beans I would make 19 10k blocks or 38 5k blocks.
Block age also matters. Older blocks become 'stale', refresh them if they are older than a month but don't reblock them all at once.