were they people who had been training a few years?
Yes.
and how do i work everything 2x/week without burning out?
You could start using a upperbody/lowerbody split, that means you train your upperbody twice a week, and lowerbody twice a week as well.
For example:
Monday: UB
Wednesday: LB
Friday: UB
Saturday: LB
Don't go to failure, going to failure DOES NOT promote extra muscle growth or strength gain, and your central nervous system has to recover a lot longer than when you don't lift to failure.
This basically means that if you benchpress 3 sets to failure in your upperbody workout, your CNS is still recovering on your second UB workout that week. No CNS recovery = strength loss.
If you don't go to failure, your CNS will recover a lot faster, so you can train more frequent = a more frequent growth impulse.
Also, by doing a certain movement 2 times a week, your motor patterns for that movement gets a lot more practice than when you would only be doing that movement only once a week.
Better motor patterns = more strength.
Another tip: don't stick too long with the same exercises, vary a lot in your workouts.
I've been training with a simple split too, but after I switched to high frequency and put more effort in the basic compound movements instead of useless exercises like flyes, leg extensions etc. then the real gains started.