Do you think itās okay to be angelkin but not believing in a religion/god?
If you're asking whether it's okay: Frankly, your personal beliefs are no one's business but yours. As long as you're not hurting anyone or advocating for anyone to be hurt, you're fine. You can have all the contradictory beliefs in the world and while I might be mildly concerned for your critical thinking skills depending how far you take that, there's nothing inherently morally wrong with that. You wouldn't be the only angel I've seen to not believe in God/gods.
If you're asking from a theological standpoint whether it makes sense/fits within a single ideological framework, that's a somewhat different question that I'm happy to help you explore now that that big important thing is out of the way. To preface this, I'm a big believer in internal consistency - basically, whatever you believe about the metaphysical/spiritual/religious, it should be consistent with itself and you shouldn't be contradicting yourself at any time. If you are, there's a logical flaw somewhere that says one of those two things must not be true, if they can't both be true at the same time. (However, things may appear to be contradictory sometimes which aren't actually when you dig a little deeper.)
Frankly, that second question depends on a whole bunch of factors, primarily 1) your personal explanation for your being angelkin, 2) how you're defining "angel," and 3) closely linked to #2, whether you believe angels can exist without God/gods. Let's go through them one at a time:
1) Your personal explanation for your otherkinity. If you think your otherkinity comes from (or might come from) pretty much any psychological source, this is a moot question; angels don't need to literally exist in any sense (physically or non-physically, in this world or any other) for you to have them as a psychological kintype. Archetypal resonance and probably some other explanations for otherkinity that are slipping my mind also fall into this category. Similarly, if you believe in a multiverse, that probably also answers your question; gods don't need to exist in this world to potentially exist in other universes, which eliminates the need for the question.
(If you simply don't know (or don't care) where your otherkinity comes from, then there's still nothing inherently contradictory about identifying as an angel while not believing in God or gods, because any one of the above explanations could potentially apply and make it internally consistent. You don't have to pin down which one of them you think it is for that to be true. It can be an "I don't know what it is, but it's probably not [x] because that doesn't make much sense" situation.)
But let's say you happen to believe that either a) you were (or will be) at some point literally an angel (whether in a physical or purely spiritual form) in this world, or b) you were/are/will be literally an angel in another world, but you don't believe there were actual gods in that world either. In that case, the question is still relevant, and we move on to point 2:
2. How you're defining "angel." "Angel" isn't nearly as broad as "dragon" in terms of umbrella terms, but it can still mean a number of things. For many people, "servant/messenger of God/a god" is a part of how they define "angel", so an angel existing in a world without at least one god to serve wouldn't make much sense - they would no longer be an angel, but something else. However, you might simply define an "angel" as a very powerful, semi/quasi-divine being that isn't quite powerful enough to qualify as a god themself. Or what you're describing as an "angel" might be even less related to the typical definition and be something more similar to air elementals or aasimar from D&D - mortal or semi-mortal beings, but with "celestial" qualities that make them superficially seem like "angels" to us (or at least make them close enough that it's a convenient shorthand to explain them). Whether that truly "counts" as an angel is probably up for debate, but there may not be a better term for it, so it may be what you're stuck with regardless.
So: How do you define "angel"? Or, perhaps more effectively: Write down a definition of "angel". Then (afterward, not before), write down a description of your kintype, with whatever details of appearance, physiology, culture, etc. you deem important, without using the word "angel" (or any derivatives like "angelic," or even "celestial" if you want a challenge) anywhere. Then reread that description, compare to your written definition of "angel," and see if they match. Try to explain (written down, preferably) why or why not your kintype reads as "angel" to you, in as much detail as you can. Hell, try to write two arguments, one for why it should and one for why it should not be counted as an "angel", if you want, and then compare how strong each argument is!
(Bonus round: send your written definition and description to a friend and see if they think they match, or send just the description and ask if it would qualify as "angel" in their mind (and why/why not, and what they'd call it if not), or send the argument(s) you wrote down for why and/or why not to them and see if they think the argument is sound/which argument they think is stronger! This is not because their opinion is automatically correct - their logic may not be sound, or you may simply still disagree with them - but getting a second or third opinion is rarely a bad thing.)
Now, hang onto what you wrote down - it's going to be important to this next part.
3. Do you believe an "angel" can exist in the absence of God/gods? Take another look at the definition you wrote of "angel." Assuming you've made it this far and aren't just reading out of fascination at the thought process, if there's anything necessitating the presence of a god in there, you have a problem. And that wouldn't be unusual! When you say "angel" to someone, typically they're immediately going to think of a being connected to/serving a god, most often the Christian God.
But there may be exceptions to that - as I described earlier, you may essentially be using "angel" as a shorthand to describe something that's not really technically an "angel", but which we don't have a more accurate word for that's in common usage - something to get the point across in casual conversation, which can then be explained further if the topic of conversation necessitates that. Or you may consider any semi/quasi-divine being not quite powerful enough to count as a god an "angel," regardless of whether there are more powerful beings present that they serve. There's some room for interpretation there, in my opinion - or there may be a word that fits that kind of being better that I don't know!
That... pretty much covers my thought process on how one would prove that out if the answer isn't immediately obvious, I think? That got Way longer than expected, sorry ^^; Best of luck figuring things out!