Should I use these surveys?
Just as long as you feel like giving a damn about your employees. The Employee Engagement surveys are there to provide anyone interested with a free tool to keep track of people's thoughts regarding their job. It can be motivation or how valued or comfortable they feel in their current occupation. This questionnaire's purpose should be purely driven by the intent to improve the conditions of the workplace and consider how could you make your employees' lives easier and more enjoyable.
Are the templates customisable?
Yeah, of course. Any of the free templates are waiting for you to pick them up and experiment with them. Not in a "big corporation putting weird, dangerous stuff inside animals to see how their poor bodies react" way, but more as in a "person discovers inner hidden passion for a specific form of art" way. Play around with the fonts, colors, design, or change the questions until you're fully comfortable and satisfied with the result.
How can I share it?
Lucky for you, that's an easy one, in this specific case. Since we're talking about employees, chances are you have a list or something of their contact numbers or emails. All you have to do is forward the online questionnaire to all at once and wait for happier employees to come in on Monday. Also, the form allows for automated notifications upon successful submission, which translates to: "David has submitted the survey" each time someone finishes it. It's probably going to show as a different name unless your whole employee base is named David, which would be confusing. But fun, I guess.