It's very different from California. In California it's not sketchy at all and legitimate services can be found on Weedmaps with their full menu and pricing and you're probably getting what they say you're getting and paying a fair price. In NYC delivery services are a criminal enterprise with widely varying levels of professionalism and quality of product. And everyone will claim whatever they think you want to hear about their product and will usually have a much smaller selection than you'd find in California and you're probably only getting a strain that looks like a popular strain from leafly not that actual strain. Stuff that's "top shelf" in NYC is usually comparable to mids at a good dispensary in California, and pricing in nyc doesn't always have a relationship to quality. Sometimes you'll get lucky with a particular strain, but most dealers don't have a consistent level of quality product. And in NYC "delivery services" are typically dealers that just have multiple people working under them and aren't all that different from a guy on a street corner. The better ones will weigh out in front of you, everyone else is probably shorting you or giving you stuff that has more stems than you'd like. Expect to be missing 10% of what you're supposedly paying for with most delivery services in NYC. It's not personal it's just how it is and most of the have enough customers that losing your business isn't a hardship.
As far as the actual experience. Most won't deliver to a hotel and the ones that will are going to be lower quality. The delivery person will not be able to make change and you must make your order when arranging the delivery. You generally can't alter that order, but some will allow you to add stuff on. Most won't be carrying more than they are selling to you right then and won't have any cash on them or only a few bucks, don't expect to get change from a dealer in NYC pay the exact price or they will just keep the extra as a tip. It's not required that you tip as delivery services cost more than pickup so it's built into the price, but if you're going to be doing business with the same person more than once tipping will ensure they don't short you in the future and might even give you slightly more in the future but don't count on that. Offer them a seat and water or a non-alcoholic drink and you'll be way less likely to be shorted. They're working a job and probably tired and/or thirsty and will appreciate the gesture. You're probably the only person who was that courteous to them that week and they'll usually remember that you were chill and treated them like a person.