steam is fine. Watch Peach's beginner guide in the guides section. She goes over all the info you need to get started and she does a very good job of making the run easy to jump into. It's not the WR route, it cuts out a frame perfect trick at the end of the run and some of the more tricky strats to make it more beginner friendly. You can very easily transition into a more optimal route later if you want to.

Honestly this game is very beginner friendly and all the necessary strats are pretty easy. Really happy to see more people interested in the run!

also I'm not like suuuper good at the game or anything and you're probably better off asking one of the better runners but if you ever have any questions feel free to DM me on twitter or discord, I'm happy to help out as best as I can!

LSD is load save displacement.

The basic idea is you enter a loading zone, pause and save during the fade to black, then you load the save. Idk the specifics of how it works but it can do a lot of wacky stuff depending on the load zone you do it in and is used to skip parts of the game and get to certain areas faster.

There is a good beginner guide for any% in the guides section. It goes over the basic strats for the game. Your friend should give it a watch even if they don't plan to run any% much.