Had lots of funny moments in my life relating to salting pasta water. Almost all the people I know put like two pinches of salt into the water. Which causes them to look at me like I'm a psycho when I pour salt in for almost a full second, straight out of the container.
I can +1 both of your tips, I follow them both since I learned to cook and they're a (small but effective) game-changer.
INB4, "save your pasta water." I don't have a big kitchen or freezer, a pot full of water is a giant waste of space for me.
As for "salty water vs. salty sauce", the better way from a culinary perspective is both. Over salting one thing to compensate for another thing often leads to uneven flavor; if everything is salted roughly appropriately it all kinda comes together without any extra effort. I suggest trying it, hell maybe even do an A/B test. It's subtle, but salt penetrating the pasta during cooking makes it taste that much better.
- Ingredients cook differently when salted. Not sure about pasta specifically: I _think_ I can taste a difference between pasta cooked in salted water and pasta salted after being cooked, but I'm not certain.
- Definitely don't keep pasta water around, it's just for the sauce you're currently making
I can't ever say I've felt like cooking pasta without salt is "under salted." Is it as savory and delicious as what I'd buy at a restaurant? No - but having done it like that in the past I just think the benefits are marginal for how much you waste.
I make pasta _very_ often, I love it and want it to be as good as it possibly can, so I'm very happy optimising for taste. FWIW I use a tablespoon of salt per portion, and get a 1.3kg pack of salt every few months: hardly a huge waste!
disclaimer: it might be /slightly/ energy inefficient.
But salt your water, salting the sauce is just not the same.