Funny kittens. OK now, training with a clicker makes you guys bond better, it wouldn't teach them not to do something. Instead it will teach them to do something else. And of course it needs time. If you want them to listen to the word ''No'', you should also train them to do stuff which gets them rewards. This would teach them that you love them but don't like when they do the bad stuff. Start training them to come by having something delicious each time you call them, also calling them at dinner (cat dinner of course) time makes training easier and they may learn faster to come to you when you call. That also means not to keep their bowls full all the time.The more you call them then give them treats or dinner the faster they will learn. In this case, saying ''No'' when they do the bad behaviour won't make them try to stay away from you. Treats will make them love and probably trust you as their MOM! So to make a long story short, if you want them to listen to the word ''No'' and still not hate you, you should also encourage them to do things that get them treats or a bite of wet food. They love wet food.
Calling them to play is also a big step to bond. You can do that by choosing a certain word such as ''play'' or ''yoohoo'' and throw some toy or ball. They would associate the word with play and so run to you every time you say the word. And if the word ''no'' doesn't ever work, try saying it then put them in their carrier for some time. And about the water spray it doesn't really matter if they know it's you, just don't use it with everything. For example use it to stop them from coming on your dinner table, to stop them from eating fake plants (although I don't recommend it--it's better to just move the plants elsewhere) and to stop curtain climbing. But give them a warning first. Say no a couple of times like 3 or 4 then if they don't listen, shoot, and if they stay, keep shooting until they stop whatever they are doing. If it's a strong sprayer, avoid the face as much as possible. Use it only at the hip or back. If it's really soft and sends sparkles everywhere it's okay to get to the face as it is annoying to them and at the same time won't hurt them. But don't intentionally aim to the face, that just ain't nice.
Do NOT chase them with the water spray it makes them fear you . When they run away and leave the bad behaviour, stop shooting. it should take 3 sprays at maximum.That makes them understand you are a strict person but they'll still listen to your rules because in other cases you give them treats and attention just for being good at what they like (basically play). That means let them have things to climb instead of a curtain and praise them for it, allow them to take a toy (or possibly some of your stuff as toy) and show them you're proud of them for choosing and skillfully biting, chasing, playing, etc. with whatever they chose.
Cats don't like to break rules even though you see a lot of them break it. They sometimes can't help it especially if it's about food. Of course you don't have to spray them every time. When they're used to it you could say no and IF necessary show them the water bottle, they should immediatly get the idea.That would make them remember the word.
BUT before starting the water spray process you should teach the ''No means I don't approve''. For example if you wanted them off counters, (if they are kittens and not overweight, never do so to a cat) hold them from the scruff and say no then put them down. Don't expect them to listen to the word ''No'' when they don't get the word. Doing the scruff thing makes them get the word. And saying ''No'' then spraying when they aren't trained to the word ''no'' will only make them see the word ''No'' as ''I'll attack you for no reason now, but i'm an idiot so I warn you every time''. After they learn''No'' you level up IF NEEDED and start with the water spray thing. Some cats don't even need the spraying thing. They'll just listen to ''No'' from the scruff thing.
You shouldn't ever scruff a CAT because cats don't have a lot of skin on their necks like kittens, and also when you try to scruff your kitten you can realize if it has enough skin to not choke or if it has a little amount of skin and so chokes which of course, you should never do. Holding them from the scruff only and not carrying them from it is enough.
By using the carrier for certain stuff and water for others, scruffing for little stuff (not so important stuff) it should workout for you. BUT still you should start with scruffing and using the carrier before spraying. Use the word ''No''for everything which you don't approve at first, then if the cat doesn't listen use other techniques. That's after they learn to love you. They will then want to do the good things to get the treats and attention (when they start craving it from you) and avoid the bad things. (By the way you could also use a word instead of a clicker but remember to say it every time they do the good behavior and then make sure they get a treat after saying it). The whole process will take some time, so can you be patient enough to handle two cute little kittens?
If you sense your cat getting sensitive about punishment, that means you overdid it. And that can ruin everything. Try to avoid punishing them as much as possible. And praising them more. Some cats may never learn--they might just get displeased with you. In such cases leaving the cat be is your best option.