Hi Sadie1123, continuing on with what Siân has said - I think the two concepts that you are looking at exploring here are different and it is important to consider a few things when you're exploring them mentally. Also, you're not a bad personal at all for being curious. It's just important to think about the motivations we have for our actions, and whether they're going to actually achieve what we think they are going to, or something else. This kind of self awareness and ability to consider our actions and their impact before we do them is an important skill to learn.
With regards to understanding your friends' experiences - it is important to remember is that part of the 'grounding' experience that you can't (and I can't recommend that you try to and so effect what sounds like a generally good relationship you have with your parents) recreate is the emotional factor in terms of experiencing a sense of discord with their parents, and the emotions that might come with that - responding to a sense of disappointment, or perhaps disapproval/anger/sadness on one or both sides of the relationship, which is highly variable depending on the circumstances that lead to the grounding (and the conditions of the grounding). Sometimes people can be grounded for breaking and entirely reasonable boundary of the family in a manner that isn't too harsh, but other times maybe the dynamic with their parents is more problematic (say someone's parents are homophobic, and so they got grounded for holding hands with someone of the same gender, the punishment might be the same but the cause would be unjust, or perhaps the magnitude of the grounding is really out of line with the boundary crossing).
The better way to empathise and understand your friend's experience in this situation is to listen to them and hear their experience. There is no way to acquire/achieve empathy or understanding someone's internal experience by 'sampling' it in an artificial manner (the tourist metaphor that Siân mentioned is a great one here, visiting somewhere is a very different and artificial experience compared to living somewhere and being raised in its culture). Instead, practicing active listening and empathy with them when speaking with them about it, rather than focusing on having things to say about your own experiences will assist you with understanding your friend's experience in their own words. This can be an important part of learning that we need to respect and listen to the lived experience of others, even if we don't or can't understand it. Also understand that they might not not want to talk about it, and how it makes them feel etc. and it is important to respect that. But if it helps them to talk about their frustration, or perhaps talk about who they broke a boundary, but feel that it is trivial/unfair etc. You might indeed feel differently about it than them if they did do something that you wouldn't, but it is important to know that their emotions are valid even if they know they did do something that they acknowledge might not have been the best life choice.
Here is something that explains active listening a bit more: How to Practice Active Listening and VeryWell Mind
In terms of seeing how you'd go with screen-free time, that is a totally fine thing to try, but best to entirely separate it from the idea of being 'grounded' as it will be an entirely different experience. It can be good to have some screen free time, and to set yourself a challenge to place your focus elsewhere, but this would be a personal and internally focused exercise, that wouldn't be informative about your friend's experience. If doing more screen free things or improving your focus is something that you're interested in, I'd recommend trying this in a more gradual way rather than an endurance challenge, which can frame it as something super hard to maintain. Instead something like trying a mindfulness meditation app (that you close your eyes or play though a speaker and sleep your screen whilst the meditation is happening) or trying a hobby that can be done without a screen, or setting a short timer when going for a walk (that you could gradually increase) are all more gentle ways to experiment with this.