Add-ons for browsers are meant to provide benefits for the user, like blocking suspicious websites, advertisements, disguising the location, or giving coupons. SearchStreamz is none of these things. The extension does not give any additional value and is useless.
What it does is, change the default homepage, new tab address and implement a different search engine. It also has some functions, which are an attempt to stay relevant because you can perform those tasks with a click of a button on any browser. That includes – a PDF file converter, calculator, currency converter, and an ability to bookmark pages.
This classifies the extension or potentially unwanted program as a browser hijacker. It can also collect various browsing data, so it is definitely not worth keeping it even if you find it somehow useful.