Correct. Right now, both servers are located in the US, so you won't notice any significant ping/lag/latency difference. However - as you said - the EU server will be moved to Europe (I think Frankfurt, but don't quote me on that).
That being said, it's hard to say how/if latency will change for you. If you don't have any issues so far, I wouldn't worry too much about lag alone. It can't get worse, it may only improve.
Geographically, I'd assume the European server would be the better choice for you, since it's quite a bit closer to you. This also means that your prime time won't be that far off compared to other players playing there.
Overall, you should try to see where your friends are playing, assuming you already know people you'd like to stick with for this game.
What you definitely should keep in mind are server downtimes, which will follow different schedule for NA/EU as stated here (you might have to try to open that link twice for it to show the proper article for whatever reason):
Tuesday (Patches)
00:01 am EDT (06:01 CEST) - EU
08:00 am EDT (14:00 CEST) - NA
Friday (Reboot/Hotfixes)
00:01 am EDT (06:01 CEST) - EU
08:00 am EDT (14:00 CEST) - NA
North American Megaserver
Tuesdays at 8:00 am EDT (14:00 CEST)
Fridays at 8:00 am EDT (14:00 CEST)
European Megaserver
Tuesdays at 00:01 am EDT (6:00 am CEST)
Fridays at 00:01 am EDT (6:00 am CEST)
After all, you most likely don't want downtimes to happen during your playing time all the time.
Normally, the game time would start from the moment you apply your key (either your game key, or the game time card key) to your account, or upon applying it when creating an account.
Though I can't give you an explicit answer specific to ESO, this is a structure shared by most paid MMOs, like World of Warcraft and so on.
That said, it should be safe buying the game now and not making an account until you want to start playing. To be absolutely safe, you could try checking with the publisher, if they respond in time.
Best Answer
I found a way. It seems it appears on the left bottom side of the screen when you launch the game to log in, and has more details in the tool tip.
So now I'm wondering if there are other ways to get the version information, through commands or API, perhaps.