Hi, welcome. I'd really recommend you take a read through the 'big' 5:2 thread(s) on this board, they are really fast moving so I tend to lurk and not post but there is a wealth of information and support on there plus some very knowledgeable posters.
You are talking about both the 16:8 and the 5:2 in your post, they are separate diets although people do sometimes combine them
The 16:8 is simply only eating in an 8 hour window (say 12pm-8pm although you can pick your own window to suit you), no food or calorific drinks outside this time, every day, so for many it means skipping breakfast and not snacking in the evening after dinner. There is no calorie restriction or rules about the types of food you eat. For me the 16:8 is useful and forms healthy habits but (as I am greedy) I wouldn't lose weight and possibly would even gain weight if just eating whatever I wanted every day albeit in an 8 hour window. But it might be worth trying, if you have a lot of weight to lose just doing 16:8 without any other changes might start you off and if nothing else it will help get you into the intermittant fasting mindset.
So for me I needed to do the 5:2 to actually lose weight (and now do a 6:1 to maintain). It's been very successful for me, I initially lost a couple of stones having been overweight, I did initially mess up my maintenance having got to goal weight, and regained a bit but I am on top of it now and have successfully maintained at a healthy weight for the last few years. It wasn't super-easy, I had bad/difficult days especially when in the weight loss phase, but I find overall this way of eating sustainable (fans like to say 'way of eating' rather than 'diet' to emphasise it's about long term lifestyle changes rather than simply something you do for a while to lose weight), I will probably eat like this for the rest of my life, and I don't hate that as an idea (obviously I would love to stuff my face with chocolate, crisps and beer every single day and never gain weight but that will never happen). What I like is that nothing is forbidden, you can have treats/alcohol/carbs/junk if you want them, you can eat out and pick what you like from the menu, someone else can cook for you or you can eat a family dinner without having to be finicky or have special 'diet' food, and it fits well into a busy lifestyle.
The basics of the 5:2 are that you reduce your calories to roughly 500, 2 days a week. Technically you can eat what you want, when you want on a fast day (FD) so long as you stick to 500 cals, but most people prefer either one large or 2 small meals a day, focusing on lean protein, and veg as this is the most satisfying/filling way. On non fast days you eat 'normally', for some people this literally means eating whatever they fancy but again, I am greedy, and it would be perfectly possible for me to eat back the calorie deficit created by the fast days, so I stick to eating to my TDEE (total daily energy expenditure) which I loosely calorie count using MyFitnessPal - again there are no restrictions on type of food or when you eat, but to avoid over eating or feeling hungry/deprived most people stick to 2-3 meals a day (some people do 16:8 on NFDs), no or minimal snacking especially in the evenings, balanced healthy meals, keeping junk and alcohol to a few days a week.
Happy to answer any questions?