S2 member already handles Login processing so you would turn Off BPS or BPS Pro Login Security. I am not sure if S2 Member already comes with a CAPTCHA option so you or may not be able to use JTC Anti-Spam / Anti-Hacker if you have BPS Pro and would also turn it off.
The Brute Force Login page code that you can use that will not conflict with S2 Member or visitor logins/registration to your site would be the Server Protocol & blank user agent code. See the beginning of this Forum Topic for instructions on how to add this code to BPS Custom Code.
# BRUTE FORCE LOGIN PAGE PROTECTION
# Protects the Login page from SpamBots & Proxies
# that use Server Protocol HTTP/1.0 or a blank User Agent
RewriteCond %{REQUEST_URI} ^(/wp-login\.php|.*wp-login\.php.*)$
RewriteCond %{HTTP_USER_AGENT} ^$ [OR]
RewriteCond %{THE_REQUEST} HTTP/1\.0$ [OR]
RewriteCond %{SERVER_PROTOCOL} HTTP/1\.0$
RewriteRule ^(.*)$ - [F,L]