Collapsing copper veins seems to still be the most popular way of going about it, but I seriously doubt that it's the most time effective, so I looked into it with some tests. I know some of you guys don't care about being efficient but please bare with.
To start things off we can quite safely say that it takes 10-15 minutes to clear the visible section of a copper vein with a lvl 1 bronze pickaxe. From my tests it actually took about 5-10 minutes, but we'll exaggerate those numbers to give the collapsing method a fighting chance and also to compensate for travel time between nodes and whatever else. Anyway, this grants anywhere from 30-50 copper depending on luck and size. Let's now also say that the average time to collapse an entire copper vein is one hour and will grant you with 100-140 copper.
With these numbers we can state that method 1 on average grants 40 copper per 12.5 minutes, or in other words 192 copper per hour. Collapsing veins however is only 120 copper per hour.
If that wasn't bad enough, for a fair few of these veins you have to dig a lot of it out manually anyway since it refuses to collapse. So instead of taking you one hour suddenly you're up to 1.5, or even 2 hours, for that same 120 copper.
I just don't see the point in collapsing veins anymore. For Silver it's 100% the move, but copper? Naw. If you think I'm wrong do let me know as I'm curious to hear all y'alls opinions.