Security and spam plugins for Wordpress

I have two Wordpress sites with Inmotion. Like everyone, I get heaps of comment spam, which is mostly sorted by Wordpress and a spam filter I use. But it seems to be increasing slowly, so I have been reading about spam filtering and security generally, and I would just like a little advice please.

1. Some people say I should use a security plugin (such as Sucuri or Wordfence), but I would have thought that Inmotion already has adequate security features. Does Inmotion recommend use of a security plugin? Do other Wordpress site owners use one?

2. Do the free versions of plugins offer enough security for a small personal site? (I'm not keen on paying what they cost.)

3. Wordpress itself offers Akismet for spam filtering, and Jetpack provides security and also spam filtering. Are these the best plugins for these purposes?

4. Do these plugins slow Wordpress sites much?

Thanks for any advice.