How many days per week?
Compared to things like football or wrestling or boot camp or war, three days a week full body is not too stressful. I think the human body can handle a ton of load and make progress, especially in strength gain.
The secret is to find the least amount of work that will provide the most gain. I have trained clean on five days a week O lifting for two years and still made progress. Then, I slid back to three days a week and my lifts jumped by twenty and thirty pounds.
But, I think you have to put the load in first. Like Earl Nightingale used to say about most people’s careers: “They stand in front of an empty fireplace and say ‘give me heat.’ They don’t realzie that you have to put some logs and kindling in first.”
Depending on what you want, of course, but overall, I would argue that three days a week whole body would be “about” right for most people. The Bulgarians and Soviet lifters did three days a week until about 1972 for the bulk of their training and did marvelous. (I don’t think, in fact, I know, they weren’t clean) Three days a week was the standard for American lifters for generations.
I have trained twice a week for long periods of time. I did this workout for a while:
I threw 182 in the discus that season with only two additional throwig workouts a week. So, yes, less does work, but again, I think I had the background to back off, if that makes sense.