Domain Help

Hey guys, I'm hoping to buy up my first few domains but I have one or two questions on getting the most effective one.

First, how important is an EMD? For one of my domains it is unavailable, but EMDx.com is available. I've seen mixed things about whether or not to go for EMDx. Any help would be great.

What is the best way to treat a hyphenated phrase? The majority of people search my keyword with the hyphen, but it is also fairly popular without the hyphen. Would you go for hyphenated-phrase.com or hyphenatedphrase.com?

Final question involves domain but any help on how to treat this would be appreciated. I have found a niche with several keywords and phrases that I think I could rank well for. Would you put this under the umbrella of the general niche, which would be harder to rank for, but make sure you are optimised on the other pages for your keywords?

Hypothetical example, lets say my niche is tennis. I could buy tennis.com but wouldn't rank well for this. However my keywords are, tennisforehand, tennisbackhand, tennisserve. I was considering buying tennis.com and working hard to rank the keywords, almost turning it into a mini authority site. Or would you recommend me buying up all the individual keyword domains and building individual micro niche sites? Or even buying the most popular one, say tennisforehand, and building my authority site on that domain that also includes the backhand and serve articles?

Any help would be much appreciated. Very eager to get started!