There are numerous topics about this and you can easily search the forums to find out all of the information. mIRC supports UTF8. That means that codepage characters are not going to be supported. Any channel you use should stick to UTF8 encoding as codepages are outdated. Basically, why have dozens of codepages that only allow you to view one language correctly when you can have a single encoding that handles all languages? It just makes sense to use UTF8.

So, the best thing you can do to begin with is to have the channel name in UTF8. All major clients support UTF8. In fact, mIRC was one of the last to fully support it. So everyone can get in as long as they have UTF8 enabled and aren't using an obscure or outdated client that doesn't support it.

After that, you are left with 2 possible UTF8 versions... capital and lowercase. Now... this is not a mIRC issue. The networks decide whether or not upper and lowercase are treated as the same thing. For ASCII, they have pretty much always been the same. For UTF8, most or perhaps all network ircds have not made the distinction between upper and lowercase characters and so every character is different and not treated as the same (other than A-Z). If you would like to have upper and lowercase treated as the same in UTF8, then the best thing to do is to bug the network and ircd developers to make that change. If enough people request it, you should start seeing it happen. Right now, few people are requesting it and if that remains the case, it's unlikely to change. In any case, mIRC cannot do anything to solve that for you. It *could* automatically change capital UTF8 to lowercase so you always join the lowercase channel, but that of course means you can't join an uppercase channel. That wouldn't be a good option.

In general, most people type in lowercase except when starting sentences or writing names. Although a channel might look more "interesting" as MyChAnNeL, you'd be better off naming it in all lowercase if it includes UTF8 characters. The same for cases where the capitalization makes it easier to read, such as ThisIsMyChannel instead of thisismychannel. Even then, you need to decide whether you want to make it easy for everyone to join or make it look "nicer." Until (IF) networks start making upper and lowercase the same, you don't really have any other options.

Regardless what you do, I'd strongly recommend using UTF8 encoding. Someday, you will have to make the switch. It might as well be today.