The list of channels on a given irc network will be the same irrespectively of the client you use to connect there.
In some cases, you may be directed to a web client that will have a single channel prefilled, or only a few ones related to the project. That's just to make things easier to newcomers.
Any IRC client will be able to connect to the channel, and everyone will be in the same room. In fact, it is often the case that the users will be connecting from many different clients, each using their favorite one. And the choice of client is something that can raise very strong reactions
https://xkcd.com/1782/ :)
Kind regards