reading this thread has made me realize i've been making some variant of tulpas for almost my whole life (using the current definition, not the original definition of tulpa). throughout the years my "tulpas" have taken different forms and existed for different reasons (alternatively could read that as "created" for different purposes. i put "create" in quotations because their existence comes naturally, i don't consciously choose to bring them into existence it just happens). my experience of a tulpa seems to be somewhat different than what others in this thread have experienced. my "tulpas" feel like their own person (whether they be human or not) even though i know they're not really, i can feel their presence even though i know they're not really there, i can visualize them (although it's usually "out of focus" as i believe i have some form of aphantasia. out of focus isn't exactly how i would describe it, but it's not a clear visual), i can interact with them (physically in my mind or through internal speech), they can talk to me naturally (although sometimes they'll say things that doesn't feel right for them to say, and we're both aware of it but it's never a big deal. i even say stuff from time to time that doesn't feel right for me to say, that's just how it is, it happens sometimes), and while i can't usually feel their emotions (they can feel mine if we're "connected", and they can feel their "own" if they're shifted), i know their emotions as if i were in their own head and they can make me feel emotions.
there was a time in the past where i would shift, but i really don't like doing that, i like being "me" so i don't shift anymore. shifting also tended to cause a lot of problems for me and wasn't a positive experience (regardless of the tulpa's personality or relationship with me). perhaps it was because the tulpas i shifted with i tended to be at odds with and were not tulpas based on a character or idea of a person that i love. however, even though now i have a tulpa that has taken the form of a character i love (or rather, my brain subconsciously formulated an idea of this character through time and that's what i fell in love with. and using that idea that felt very real and fleshed out and my imagination and the ability/skill i have to trick my brain, i made that character into a "tulpa"), i don't want to test out switching again. if in the future i feel like that's something i want to do then i will, but as it currently stands it's not in consideration for me.
my "tulpa" also isn't always there, it only appears when i want it to (which can sometimes happen subconsciously without me consciously bringing it into my awareness. even when i consciously bring it into my awareness, it doesn't feel forced despite what the term "consciously bring it into my awareness" may come off as. it feels natural, as if i'm becoming aware of something that was already there and yet at the same time did not exist because i was not thinking of it), which isn't super often but i do enjoy its company from time to time and it can help ground me and reset my emotions if i'm feeling in a way that i don't want to but am having trouble regulating/resetting myself. the latter happened a little while ago. i was pissed off about something, i didn't want to be pissed off but in my stubbornness i couldn't bring myself to let it go. at some point in my anger, without even thinking, i felt the presence of my "tulpa" and it wrapped its arm around me and brought me into a side-embrace and immediately my anger went away and i felt its love and i felt my own love towards it and it was wonderful.
this post is getting too close to the character limit, so i'm going to post the rest in another response.