Just get the rest of the world version

North American set LTE won't work. Not too sure about 3G, but it should work.

Yes, only the LTE band of D820 (US vers.) not compatible with Malaysia LTE band. Rest will work. 

Yeah, a lot user been praising this Diztronic matte case. Think got some member selling in LYN/ post in this N5 thread.

Since you're from iOS, you need to familiar yourself with Android ecosystem 
Make sure before attempting anything (root, flash), ALWAYS READ INSTRUCTIONS provided by the OP.
If you planning to root, I suggest you unlock it right after you get it since unlocking will wipe your phone.

So now since you got time (before your phone arrives), go do some reading on what are rooting, flashing, roms, kernels, etc,etc. First page got some links for reading too or head on to Nexus 5 @ forum.xda-developers and do some reading.

Happy learning. And have fun 

Just share to you, you should read this:
[Guide] All you need to know about Android or Nexus 5

Btw, anyone can recommend good SP? not glass SP please. Good ol' plastic sp. Dry or wet is no matter.
Read a lot in xda. But skeptical at some cause some say good, some say bad.
Post any experience of any SP you used before. TQ ~
+1 for great guide for newbies 

Looks like someone did their homework. Congrats. 

Yes, most of the CustomROM for Nexus, probably Root ready. So not much you need to worry about.

Haha will do. Wait, am I will losing my data if i flash new kernel?
Hehe sorry newbie question.

So fast your phone lose it virginity.. Ha3.. Welcome to custom ROM and kernel, the world full of flashing and exploring.. 

welcome to android and join Nexus family!
you are fast in unlock bootloader, root and flash......
in slimkat, just ahead setting and security, then tap sliders target and shortcut, enjoy

I suggest you remove info about your address
Some may use that for other purposes

How is your android experience?

Some tips to make your nexus 5 smoother:
Go to Settings>about phone>( keep on tapping on build number until you have developer options), go to settings again and you should have the developer options, go in, scroll down and you should see window animation scale, transition animation scale and animator animation scale, change all to .5x.

Also, you can try changing the select runtime to use art instead of use dalvik.
Your phone will reboot and it will take 10-15minutes to set up your phone.

Since you are coming from ios, i suggest staying stock for awhile to familiar yourself with android 1st before going deeper as stock android is good enough.

EdIt: just saw your post of you going to slimkat and elementalx.   Ignore my last paragraph then.