First off, welcome to the wonderful world of CoG! My name is @fantom and I’ll be your guide for the evening!
Word count varies quite a lot in Choice games. Hosted games, which are made by experienced writers typically, I’ve noticed tend to clock in at about 200,000+, though some are lower like in the 75,000 or so range. Hosted games, which more often tend to be first time or beginning writers, tend to range anywhere between 50,000 to 150,000, though I think the record is Tin Star with 1.2 million words. But there have been some fantastic ones with lower word counts.
As for the second question, I believe @poison_mara writes on an iphone using dropbox and such, but it is more difficult obviously.
As for cover art, I’ll just quote the wonderful @Lucid
