This as far as I remember has been discussed other times already, and the general consensus is usually that traffic would be reduced a lot.
If you compare this data with any other board, you will find that by removing signature campaigns, the number of content in the forum will decrease by an estimated percentage, and 95% of accounts may stop posting.
Most likely. Signature campaigns incentivize posting, and just as they can incentivize posts of mediocre quality in the Gambling section, for example, they also incentivize posts of great quality.
Many of the people who use their time in this forum and earn money, if they stopped earning money here they would surely find ways to earn money elsewhere on the internet, so it would be normal for them to leave this forum and dedicate themselves to it.