Great topic!
Pre-lockdown, I was going to the gym (and sauna!) 5 days a week and in the summer I go for long walks up the mountain.
I also experiment with different diets - I love seeing how the various types impact my health and I found that a Palaeolithic-type diet suits me well. Currently I am experimenting with the carnivore diet (again!)
In the gym I do mostly compound exercises and I would agree that body composition is 80% diet - but that 20% exercise is important too. I feel we should always try to mimic what we have evolved to do, so in other words what our ancestors ate/did… even if just as a starting point. This includes lifting heavy things and sprinting and even doing things that scare us a little bit or get our adrenaline pumping!
I also think the microbiome is more important to human health than we currently realise - only 10% of the cells in/on our bodies actually belong to humans, the rest belong to microbes/gut flora etc, collectively known as the microbiome. When this gets out of kilter, many diseases can follow.
My best advice is usually to try things for yourself. Do research and try what makes sense to you 