* Is there a sticky explaining the differences of airdrops vs bounties vs signature campaigns?
I dunno if there is since you can easily know it once you will see a thread whether a bounty, airdrop or signature. But to sum up, all of them considered as bounties, you will be rewarded some altcoin/token after doing a job (simple or not).
Different campaigns made by the project is considered as Bounties, such as signature, social media (including twitter, facebook, reddit, linkedin, etc), content creation such as making video and articles, translation campaign and etc. As airdrops are like free, but mostly its altcoin/token distributed by the team after doing some simple tasks such as following or sharing their social media accounts or etc. Signature campaign is wearing signature in your signature space obviously, either paid via bitcoin, altcoin or tokens and considered also as bounty.
* Do they favor my status (Jr Member I think I am) ... I know that higher statuses earn more at this point
Most signature campaigns paid with BTC accepts only from member rank above but there are some campaign accepts jr member but they're rarely posted. But bounty campaigns I guess accepts from jr member.
* Can you participate in more than one?
If you're referring to bounties like in social media campaigns, content creation, translation, etc. yes you can but if you're referring to signature campaigns then most probably not.
* If you post here everyday as a habit, what's the level of extra effort involved in participating in bounties and signature campaigns?
Nothing, you only get more number of posts but in the other hand, you will reach the quota of your signature campaign(if ever you have joined) faster.