Hello!
There are even several active communities, and this one is the newest, created specifically for Heroes 1-2. Here you can also find some aspiring fan projects for the game.
For launching Heroes 2 on modern systems, feel free to visit
this topic.
For obtaining a universal playable version of H2 visit GoG.com.
For other HoMM2-related content you can go to homm2.com.
Concerning the tournaments, currently it's hard to find
online tournaments because one game in Heroes can take weeks. The majority of the tournaments are
offline - this is another tourney type which intends offline play and usually held by Russian HeroesPortal.net or Hungarian hommm.hu. Occasionally there are some more tourneys from other sites going on. Online players can connect in ICQ or GameRanger or whatever, but currently there are no 'official' tourneys going on on any of Heroes 2-related sites. The last online tourney (for Heroes 2) on HeroesPortal.net was in 2012, for example.
Offline tourney is a tourney where you download a pre-defined savegame and try to fulfill the tourney victory conditions with the best results. The most common victory condition is the least number of days to finish a certain task (it's not always winning the map). After that, a final savegame is made and sent to the Tournament Master of the hosting site.
There are different types of offline tournaments, and I can explain it later if you're still interested.