Ok, I play older metal (Death, Metallica, Megadeth, Slayer, Morbid Angel, etc.) but I'm usually in E standard tuning. Recently I've started tuning a whole step down to D standard because of my love for the band Death. How does this effect tone, strings, picks etc.?

1.) What gauge strings do I need to play in D standard so they're not all floppy

2.) Do I need thicker picks while downtuned?

3.) Does downtuning effect tone? Do I need to resetup my EQ for my new tuning?
1) I would definitely suggest 10 or 11 gauge strings.

2) You might as well. I suggest Jazz III Dunlops.

3) Depends, you may have to tool around.
You definitely shouldn't need thicker picks because bass players often use similar gauge picks to guitarists, such as me for example (dunlop .73mm).

EDIT: I play bass btw