I wouldnt purchase anything that you dont already have the room for. I'm kind of a hypocrite, when I say that, as I have a Whitemouth Moray (4th pic) in the 200gal. and Whitemouth's max out around 5'...so, I'll have to move him to another/bigger tank. But, I got him when I first got into the hobby, as a newbie mistake. If I knew what I know today, I never wouldve gotten him.
Fimbriated Morays grow to aprox. 32" - 36" and are killing machines. A buddy of mine had one that was aprox. 30" long and it ate an 8" Volitan Lion.
I'd suggest getting the tank first, and then choosing what fish you want.