What settings will it change if I press reset all settings on my iPhone?

Also, will this help speed up my iPhone because that's what I've heard. Because my iPhone has been so slow lately and taking like 3-5 minutes to send 1 text. If you know of any other ways that could help speed that up please also let me know that.

If you reset it, everything you set in settings will restart such as passwords, ringtones, walpaper, and if you connected to Wi-Fi and the slow text has been happening to a lot of iPhones and they've been having recalls on iPhone 4's

All of them them of course. As the name suggests. No that will not speed it up. You could try to do a restore.