Confused after long absence...

Hello there!!

My wife and I recently started playing magic. I played as a kid (2003-2005) and have two precon decks that we have been playing with. One deck is 40 cards, the other 60. I added a few random cards to the 40 to get it up to the 60 amount.

We are looking to buy two new decks for ourselves and I was hoping to get precons similar to those I bought way back as a child.

In looking to buy I am confused about the different styles, deck sizes, etc.

Is 100 cards the new standard? Should I ditch the 60 card decks? Are Planeswalkers the new norm, are they compatible when playing against my old decks? Too many options!!?!

Any help would be much appreciated, thank you!