Wins per Level Data Availability?

yes, yes, you can hoard more games if you giveaway some trash

Of course there's a better chance to win a high level GA, because less people are able to enter those. It's quite logical ;)
If a GA has 1000 entries, chance for everyone to win is 0,1%. If a GA has 50 entries, chance is 2%.
Just check out higher level GA's to see how many people enter those.
My only win so far was a level 2 GA. That's the highest level I can join atm.

Level doesnt really matter all that much.

The only benefit level gets you is entering those high level GA's .

Obviously the higher level the GA is the fewer people will participate in it = Higher chance to win the game.

But if you are unlucky you can be level 50 entering GA's with 2 ppl in it and still not win anything :)

Pray to the RNG God every time you enter a GA and you should win :P

You may find it easier to join private giveaway groups with a higher level, that's the main way your odds would increase. If giveaway group X is looking for new members, and you have given away only a few bundle leftovers, they might assume you'd just be there to leech and pass you over...

And I'm sure you already know this, but in case someone else misunderstands - everyone in a giveaway has the same chance to win. If a "level 0" person and a "level 10" person enter the same giveaway, both have the same chance to win it. :)