After install, will all settings default to "active" or "inactive"?

I might want to start with only a few options, the url rewrite for example.

Most settings are enabled after installation, but you can alter them at will. mod_rewrite settings are on, however the options to pull the topic titles and member names are disabled, as they inherently add resource overhead to do the rewriting (not much as you can see here, but more than not doing so). Using forum names does not add any real overhead since I get the names from a cache rather than the database, but it is disabled for consistency with the other two.

It is highly recommended that after installation you look through the settings to determine which will work best for you.

"It is highly recommended that after installation you look through the settings to determine which will work best for you. "

Work Best? That is affecting SE results or what?
How can you check that in practice? Enable one , check results, encble second, check results ... this way?

Well, most people stick to pretty much the same settings, however one person may want the inflated stats enabled and one person may not. One person may want to use dashes as the URL separators while one person may want to use underscores.

That note is merely there to remind people that they should configure the modification after they install it.

ok, thanks