How often is "often"? How user-friendly are these speech synthesizers? How expensive are these products to begin with? We can't assume favorable answers to those questions, so this doesn't give us enough information to strengthen.

Hardware and software were potential barriers to access in the author’s argument, since it’s not a given visually impaired people have access to these tools. This tells us they do have access to those tools, thus strengthening.

The author is simply stating the visually impaired people will have easier access to more information. Whether some people would generally prefer to access information a certain way isn't relevant.

This weakens the author’s argument by stating that most visually impaired people will have access to little or no new information on computers.

This doesn't impact the argument for two reasons. First, we're talking about current accessibility, not the future. Second, we don't know how this compares to the speed of information becoming available digitally.