It’s hard to come up with good statistics on this. For one, it’s hard to draw the boundary of this category (ex.: type and level of activity).
[...] Scammer.info has about 20,000 registered accounts and BobRTC has just passed the 30,000 accounts mark although it needs to be said that there are probably lots of fake accounts and inactive accounts. Also, there are maybe many scambaiters who don't have an account on these websites or have accounts on both websites.
Jim Browning's Discord server: 4,100 users
TLS Discord server (belonging to the website scammer.info): 8,200 users with 1,400 being online as of 2020-08-07
In both servers there are duplicates meaning they are on both servers. Also, there are lots of fake accs and inactive accs. Also you have to consider that many people on Jim's server here are not necessarily scambaiters, they're fans who watch the videos but don't engage in scambaiting itself. Same goes to Kitboga's (another popular YouTuber) Discord server . I don't have the numbers right now but his community is basically 100% fans only and non-scambaiting related.