i am trying to not use unofficial plugins because i am afraid of disadvantages or performance issues, what are the disadvantages of use unofficial plugins?
It depends on what the plugin does. In some cases it you could have better performance using a plugin rather than implementing the same thing without a plugin.
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I don't think that a well written plugin will drain your performance that much down. However there is always the possibility that the plugin will not be developed further, so you won't get updates for it (in rare cases, when changing something in C2 breaks some plugins, you can get stuck there, but as I said, it's rare). I would suggest, go with the vanilla C2 and if you feel that there's something you can't do with the basic tools, just use a plugin that has at least a few satisfied users. There are a lot serious, great plugins here
I had a similar attitude when I first started using C2...but honestly, some plugins are such time savers it's hard not to use them (litetween, magicam), or offer powerful functionality that C2 still lacks (Paster/Canvas), or, in some cases, exceed C2's internal capabilities in both features and perf (the incredible Chipmunk physics).
Ultimately though, it's your call.
I think a bigger problem is the updates of those plugins!
Official or 3rd part plugins are the essence of C2.
It depends how you do implementations, in that case if you improperly use of canvas, you get memory leak.
If you need a new feature in C2. Make or use a plugin. Do not use the event sheet to handle that. Try to only use the ES as interaction events between Plugins.