It's fine to use this form in informal contexts. Website communities such as italki tend to be informal, so it's fine to say 'Thank you guys' as a response to other members here. This comes over as something friendly and natural. In the spoken language, you might use it to friends, people you know well, and younger people. But I think it would be disrespectful to say it to strangers, especially if they are older than you. For example, I'd find it rude if a waiter in a restaurant addressed a group of customers as 'you guys'. Many learners of English presume that 'you guys' is simply the plural form of 'you', and imagine that it can be used in all contexts. It isn't. The grammar of modern English makes no distinction between the singular and plural second person. 'You guys' is a colloquialism, originally American but increasingly used worldwide. By all means, use it here on italki, or with your friends, but be aware that it isn't appropriate in all situations.

You'd use "you guys" if you were familiar with those people and they were comfortable with you using such a phrase. The key here is "familiar" - if you don't really know those people well, then it can come across as rude. You're suddenly assuming a close friendship without asking the other person. If you want to be on the safe side, just use a regular expression such as "thank you". Yes, this is perfect for addressing several people, and this is exactly what native speakers do.

'you guys' is very colloquial. I wouldn't describe it as rude. However, it may not be appropriate if the people providing corrections are female! I am not a guy!!

Okay, thank you for answering!

It's perfectly fine to use "you guys". It's just informal. Like Hilary said earlier, just avoid using it with women.