Yes agree any deescalation tips like NVR are helpful. A lot of the advice in Big Baffling Behaviours is like this. Conscious Discipline very good for this also.
Having a boundary while being kind is tricky if you're thinking of a boundary as being a sort of line which if they cross you have to give some kind of punishment. That will absolutely escalate, it's like a red rag to a bull! It doesn't help to think of it like that IME. One of the biggest things in Sarah Templeton's book is about establishing that you're on your child's side. You can't do that if you're constantly set up in a situation where you're basically daring them to cross the boundary and then (metaphorically) slamming down on them when they do.
Think of boundaries as things you can control like - console time starts after chores are done (or whatever it is). For any screen thing you can put some kind of control on it these days. If you have to go old school - hide the remote, plug, charger, or ask for the device to be physically handed in so that they get access to it again tomorrow. Or learn how to disable things off the wifi. (Google e.g. BT router controls 2025). Ideally, make a sort of contract/agreement together and then use the tech controls/parental controls as a sort of reminder of it, rather than using them as the hard limit otherwise they will just find a way around it. But at 10 you're still just about within the territory that you can go over his head if you need to -you can work towards a more collaborative system once the overall temperature in the house has cooled down, IME. First priority is reducing direct conflict.
This is why a structured behaviour system works better, as well, because then it isn't you making a decision in the moment based on how pissed off you are, which will always be perceived as an attack. It's clear - meet these expectations, get that reward. It's not a battle of wills, you against him. It's you AND him against the chart or the rule. Don't meet the expectations, I can't give it to you this time, but let's try again next time. Making it low stakes and lots of chances to try again also helps build resilience against failing. I know I've struggled before with reward type things because I feel so hard for my kids when they really really try and they don't get it. I feel like a total monster. I've read all the stuff against reward charts. I feel like it goes against so much of the stuff which is important to me like support/skill build/scaffold - but OTOH I've also found that "I'm sorry, you've lost it for tonight, but we can try again tomorrow" is an absolute gamechanger in terms of showing them:-
There IS ALWAYS another chance. Very, very, very few mistakes in life are irreversible and permanent. In ADHD this is SUCH an important message to learn because their feelings can be so very big and overwhelming and losing/failing is so hard. I feel this myself which is why I struggle with it.
I can give a clear message about the behaviour without losing it myself and displaying some totally inappropriate behaviour that I don't want them to copy. I remember the very first thing I ever used this "We can try again tomorrow" on which was when my eldest, then four, used to play absolute hell at bedtime, taking HOURS to go to sleep which I now realise was because he genuinely didn't know how to relax in order to fall asleep. Sometimes I would get SO ANGRY with him and it would be awful and I would absolutely not want him to think that the way I ended up reacting was OK. I felt guilty on the night I walked out (to him crying) saying no, sorry, that's all your chances, we can try again tomorrow - but I felt less guilty than the times I shouted or cried, and he actually fell asleep faster as well.
And, that you believe in them. That you truly know they can do it. If you're focused on what they've done wrong and lecturing them about it, then they can build this image of themselves as a terrible person. Most of the time they actually know why they shouldn't do that thing. If you're focused on "Try again next time" and/or well done for the things they have got right, then it's more neutral or even positive. When I was in the thick of it with DS1 we used to have these talks at bedtime where we'd go through the rewards he wanted to aim for the next day and sort of work out a game plan for them. It completely changed the narrative and was brilliant.
For ADHD, it also keeps the goals much more focused and closer. "I have to be good and keep my temper forever and ever and ever and never hurt anyone ever again?!?!" - this is impossible because it's much too big. Or they've failed once and so it doesn't matter if they do it right now because they've already got into trouble anyway. "I have to keep my temper just for this afternoon" - this is MUCH more doable. And plenty of repetition of this afternoon, that evening, this morning, this school day - all of this is building all good practice and highlighting their successes and it's not undone by the times where they didn't quite make it, because they are all separated out. And somehow it comes to a point where of course they can imagine never hurting anyone ever again because it's normal and easy for them to avoid it by managing conflict and frustration in other ways.
But also, I have thought about it a lot and there is really no reason that you can't work on skills and scaffold, adjust expectations/support relative to their current mood, and understand that they are having a stress response and deescalate, while also having a behaviour system in place. I do think you need to calibrate it carefully and reduce or break down the expectations if they are having trouble meeting them. Arguably, you don't need any behaviour system if you're building skills and problem solving (and I also love the Ross Greene approach, and think there is a huge huge argument for increasing kid autonomy but that would be a whole other post, although you can also certainly involve your child in setting up the rules, goals and rewards) - but if you're currently frequently getting to a point where you're (both parents) losing control and doling out punishments or even yelling horrible things because you just need to DO SOMETHING, then a behaviour system gives you something TO DO to replace that, and I think that is an enormous, enormous thing, an extremely important one and one which is sometimes overlooked by some advocates of other methods. Some people continue to use a positive behaviour system until their children are adults and don't need it any more. Some people use it as a stepping stone and once they are more familiar with more collaborative methods they find they don't need it any more. But I think it's a really helpful thing which does not need to be presented as a choice between this or a more collaborative/bottom up approach.