The thing that I think you're missing, is there are multiple steps to the K-1 process. First you file your I-129f petition, you wait for your case to be adjudicated either with an RFE, approval, or in rare cases a denial. Once approved, your case is sent to the national visa center which is essentially just a mailing center for K-1 (but they do a lot more for I-130 CR1/IR1) which sends it off to the consulate. Montreal then sends you P3, which is a pre-interview checklist to ensure you have everything you need. Once you reply to them with the information requested in the P3, they send you P4. That can be same day, or it can be a few weeks. P4 allows you to book the interview. My wait was about 5 months for the interview, and it would've been 4 but I had an issue with the consulate. They ghosted me, despite having only sent 2 emails. Weird. But we resent it on my Husbands end and got our P4.
As you can view from my timeline
My I-129f was approved in 367 days from my NOA1 date.
My interview took 521 days from my I-129F NOA1 date.
There wasn't a huge extra wait for my interview, and I still am a regular chatter with a bunch of other Montreal peeps whos timelines are very similar to mine, and more recent.
I-130 is similar, but has a different NVC > Interview process which is longer than K-1's NVC > interview. For the I-130, they actually ask stuff for you at NVC and whatnot
I couldnt do I-130 because of covid, I couldn't leave Canada because there was a mandatory hotel quarantine that was costing people around $2000 at minimum in my area. I can't afford that, we had enough money for all visa expenses and the while of time I cannot work, but what we didn't have is "just because" money. We had no idea when Canada was going to lift those restrictions, so we filed K-1. The restrictions didn't lift until months later, so I am still confident in that choice but I do wish I-130 had been possible.
K-1 has sucked. If I leave out the part where they processed me as a b2 on entry, then it's still been a heap of trouble.
Trying to get on my husbands bank as a joint sponsor, they kept trying to input me as a citizen. I kept telling them the importance of them NOT doing that, I'm not a citizen and I don't want false claims that I am literally being on my bank account, that sounds really dangerous. But time and time again they kept calling to check if citizenship was the right box, and said that they didn't have any other options because I don't have an ITIN. Eventually, they called some supervisor and was able to resolve that. When my husband and I were quoted health insurance, we searched all around. The cheapest we could find was like $250, with a 9k deductible and doctor visits not covered. I'm pretty young, so unless something absolutely devastating happens I am not frequenting hospital visits, nothing I do would even reach that 9k. We don't have that kind of money for a possibility. The only viable option, or the one I thought would be fine, was $500 and it had doctor visits, prescriptions, and I forget how much the deductible was but it was significantly less.
The issue is, we don't have an extra $500/month to put towards health insurance! On a k-1 you can't work for awhile, so that's Rent/mortgage, health insurance, car insurance, food, and care products all on one persons pay. Many can afford that, some can't. It hasn't been an issue in my marriage, even now i'm not working to further my career despite being able to, but it is an additional stress for something that could feel very preventable if you were simply able to work! Not all jobs in america provides good health insurance either, my husbands work covers something so little that im surprised they can even call it health insurance. $150/year towards wellness checks, like.. $100 per overnight hospital visits...
Another big issue, is no travel permission. I have seen many cases of people who entered on a k-1, realize one of their close family members is dying. Even with an expedited I-131, they didn't get it in time to say goodbye. That's a real possibility, you never know what could happen and how fast USCIS will deal with it. There's something really hard about being the beneficiary, unable to travel knowing each day something could happen to your childhood dog, or your parent, or sibling, or friend, and not be certain that you'd be able to be there!
I feel so happy each day that I got my GC before anything bad happened, but not everyone is as lucky as I to be able to say that.
Hope this helps, K-1 is a nightmare and I hope that whatever path you choose, that it turns out great.