Hi there! Welcome to HubPages :)
First of all, you can select the topics. Take your time to pick what suits best :) No rush...
Secondly, there is no maximum words but do bear in mind that 400 - 1,500 words are ideal. I think below 2,000 words should be just fine :)
Lastly, of course! Add links, photos and whatever possible to make your article more interesting!
Good luck in writing and god bless :)