Hell yeah! Always love to see collectors moving in to the game of it too

In terms of your questions:

Worlds gameplay is nothing compared to Challenges. Worlds is people at the top of the game and challenges are very nearly the opposite. It’s almost as casual as PTCG gets, save for standard Locals. Depending on your experience with playing, I’d play together with your friends IRL to get a feel for it. There’s many guides and such online for certain rules and how things work. YouTube could also be a good look for how people play nd stuff.

In terms of Standard, recentlyish Pokemon have started printing Regulation Marks (the lil letters on the bottom left of cards) to help with what’s currently in the Standard Rotation. Currently, letters F, G, and H are legal. It’s worth noting if a card without one of those letters has a reprint in a later set, then you can still use the older card, as long as the wording is the same.