Hi, thanks for your questions. There is much to unpack, so I’ll do my best to give a quick but concise reply.
TZM is a leaderless movement. So there aren’t really people with more authority that have this role. We’re all advocates of this Train of thought. But I do get what you mean, there are high profile people in TZM and what they say and do is getting more attention and has more influence, such as PJ. I’ve heard Peter Joseph talk about Greta and XR a few times in his podcasts, don’t know the exact episodes, sorry.
I was at a systems change meetup a few months ago where XR and Greenpeace were as well. The rebellious acts they do may have an impact towards change. But I think it’s more important to provide the understanding of why we need change and how to arrive at meaningful change. From what I gather is that the actions are impulsive and based on emotions. There isn’t really a plan besides “just stop oil”. Which is a shame, because to really change something, you have to make the old way of thinking obsolete.
Here is some more info about that day.
10 years ago this was also suggested by PJ in his blogtalk radio, to call in on other radio shows and things like that. Times have somewhat changed. Podcasts, Shorts (TikTok/YT/Instagram) and longer more detailed videos on e.g. YT would be more of our focus today. We have plenty of examples in podcasts, lectures, interviews, and Videos. I’ll start my own YT show as soon as I’ve finalized some technical things.
If you feel like politics is the way forward, then by all means, explore that possibility. It may be a little ambitious as a first project/goal. Even smaller scale projects can be a challenge with the amount of active people we have. There are some examples in Projects.
I’m not really sure what you mean here. But yes, it’s best to focus as local as possible, as long as there are people in that scope. If you have a few people in your own town, then it makes more sense to work with them then with people at the other side of the planet. Local activism is the most effective. But of course, through the Internet we can all work together. There is no rule against it. And if there are only a few people active in your country, then it makes sense to work on a national or international scope. But these chapters can overlap of course. It’s just a means to find each other and organize. Communication is key of course. That’s also why I created this forum and chapters map so we don’t become (more) fragmented.
Yes you can! 
We have quick start guides which includes the app.
Yes you can, there is no paywall or subscription needed to join it. On the forum we have chat as well, but it’s only enabled when people have reached trust level 1 and higher. Which you can get by being active for about 15 minutes on the forum. This is to make sure people don’t get overwhelmed by the features, but also because chat is harder to moderate.
No worries, the mods can easily move and edit your topic. Feel free to make mistakes, it won’t be a burden at all 
Again, welcome to the forum! 