This shouldn't be necessary, but I feel the need to put out a gentle reminder:
If some perfect stranger approaches you on the street and invites you to something without knowing you at all, yes, that is an unusual thing to do and you should treat it as such.
Every few months or years, reports of this or that organization (there's more than one, with more than one intention) trying to recruit people through random street approaches start cropping up. It's a problem around the world but seems to me to be particularly bad in Taiwan, especially in Taipei (but that could be because I don't know other cities as well.)
No, the rules are not different because you're in Taiwan - if you're new here, Taipei is a normal city full of normal people who don't approach total randos to see if they want to attend some event. They have their own lives and their own stuff going on, and don't live to just befriend totally new people they know nothing about. That's not a thing anywhere. You wouldn't do it in the country you come from, so don't do it here.
If you would do it in the country you come from, good luck to you, but I'd advise against it.
And no, this isn't a thing that happens because the Western community in Taiwan is small. There are friendly fellow foreign residents who, if they meet you under normal circumstances, will be happy to make a new friend and show you how things work here. But they do not approach you out of nowhere on the street and they don't just happen to have fliers for whatever it is they want you to attend. They carry those on purpose, to find people and get them in the door. It is intentional - they are not new friends you made because of some happy accident of timing. They aren't just super nice people who keep their eye out for Westerners who seem new to help them out. Of course they seem nice. Of course whatever they are inviting you to seems cool, or just a chance to make new friends. Of course they seem really empathetic, perhaps to the fact that you're new here and don't know many people yet. That's the point. It wouldn't work if it didn't seem like a great opportunity.
It could be some "direct marketing" scheme, it could be some religious or spiritual thing, it could be whatever. It doesn't matter. It's no less unusual to approach strangers here than anywhere else. Same for parties and other gatherings. Normal people get to know someone first: if the purpose of the interaction seems to specifically be to invite you somewhere or show you some new product, and not to get to know you as a person, that's a sign. Heed it.
If it's a marketing/sales thing, then no, it's not an amazing new product. No, the way people sell things isn't any different here than anywhere else.
If it's "free lessons" - guitar, English, Mandarin, whatever - but the person inviting you doesn't know you, no, that's not how you get music or yoga or Chinese lessons. They're probably at a church or temple.
If they are nice white guys on bicycles wearing ties, no, nice white people who want to be your friend won't stop you at a traffic light, that's weird. They want you to join their religion, not to be their friend with no strings attached.
And if it's a religious/spiritual thing, no, it's not because you're in the "East" or whatever and so people are, like, so totally more spiritual here and they want to share that which is why they are so nice.
That's not a thing and it never has been. If you're into Dao or Buddhist philosophy, good for you. Enjoy! Even so, people who share your interest in these things, yet are normal people with normal lives, still don't just randomly go around inviting strangers to things.
Please keep that in mind.