Opening against 1.d4

If it's your first OTB tournament, then the only 1. d4 opening you will encounter is the London System, so better focus on that.

Englund is a lot of fun in blitz and even quite effective. However: using it in OTB is just bad. If your opponent gets enough time to think, it's just a really bad opening.

If you're looking for inspiration, useful openings to try out as black are:

Queen's Gambit Declined
Grunfeld Defense

Yes I know, those both contain a huge volume of theory. But you know what: there's a reason for that. They're good openings. And if you're going to spend time learning openings, you might as well learn openings that continue to be useful as you progress. Knowing Englund theory is just completely useless if you're playing OTB.

nh6

I'd say Dutch defense Leningrad variation, its close to the KID, expect the f5 pawn.
www.youtube.com/watch?v=ogmGNIk6W7I

I can only recommend the Schlechter Slav. Solid like every Slav, dynamic ideas from the Grünfeld, White players are usually not well prepared. Can you want more?:)

I usually play the Slav Def.
I think it's a very good defense. And it makes sense.