Is Kinky nl credible? And is it safe to meet the girls?

Yes and Yes.

As with everything, your millage may vary.
Ebay for sex.
Kinky.nl worked when the windows shut down.
Some girls love working out of their own place, on their own schedule. They like Kinky.
Some girls hate dealing with the calls and texts, the no-shows, the drunks...and quit kinky.
I don't know how things will change, now that windows are back, but Corona helped Kinky.
There are some good girls that have been there for a long time.
Watch out for the "only in town this week" stuff.
There were some Russian escorts that would cycle in and out of town using Kinky.
I'm sure there are groups from other countries that do the same.
They generally have highly air-brushed professional photos, and sometimes link back to website run by a foreign escort service. I would avoid these.
There are plenty of girls that won't return to the windows after the last 2-3 years.
If the city ever manages to put an Eros center out in the middle of nowhere, Kinky will grow even more.
It is far from perfect, but I think it is worth learning about, just in case something horrible happens to the windows-again

Weasel

Are there other sites like kinky that you could recommend? Ik ss is a thing, but its a bit expensive for me. And how does the booking works in kinky? And should I ask the girls the types of questions you would usually ask when at a window? In order to make sure I know what I'm getting for what price?

Kinky is by far the biggest site that I know of.
Escort sites will have 20-40 girls.
Kinky lists several hundred.
Meets are usually arranged by text or Whatsapp.
You can ask some basic questions, but if you go overboard, they will just stop responding.
The more professional girls put most information in the ad. Read carefully.

Weasel

Sounds like you have used the site before, are there any girls you would recommend?

I looked at eurogirlsescort and the site seems kinda sketchy. A lot of reviews claiming the women hang up on them after they sent money, or that they're not the same ones from the photos. Anyone know a good, credible alternative to kinky nl?

Well I would never send money in advance. Always do the transaction on meetup. So if the girl isnt the person on the picture, ill just refuse them.

I'm not sure how many girls would be willing to do that though, most escorts need a deposit in advance. But yeah ideally I want to pay in cash, in person, to keep things direct and private. If anyone here has experiences hiring escorts in Amsterdam I'd like some advice too.