Hi Stroid,
The main competition on these A&A forums is the Global league. Here at these forums the league competition was mainly Revised until 2009, then AA50 till like 2012, and Global since then. If you love Axis and Allies I encourage you to download TripleA and/or buy Global and check it out.
The A&A community is a bit disjointed in that different groups/communities play different games. I imagine GTO is mainly Revised and 1942.1 (the 2008 version, not the current 1942.2 version). If you want to play other versions, I reccommend downloading the TripleA freeware.
I started out playing on GTO but I learned to play other formats (eg TripleA and Battlemap) because I wanted to play AA50.
For f2f tournaments, see
http://www.axisandallies.org/category/events/
http://www.headlesshorseman2.com/id11.html
If you are willing to learn Battlemap (the old school map program that we used here until recently) then there are other clubs who hold tournaments you can participate in.
See
AAMC
http://www.aamc.net/
IAAPA
http://www.axisandallies.net/
And AAWC, which uses the “3rd edition” ruleset from back in the 90s, before Revised.
http://axisandalliesworldclub.net/
These are all great clubs with expert players, but imho the most cutting-edge A&A competition is on these forums. To participate, you no longer need to learn how to use Battlemap–you just need to use TripleA, which is easy to learn and much better software than GTO.