Pyxel Edit edit snaps to the same lines if you Shift+Pencil to draw a line, and hold Ctrl to snap. Aseprite's Line tool + Shift lets you snap between horizontal, 1:2, 1:1, 2:1 and vertical. You can do pixel-isometric (not actually 30º, but 1:2 lines) in any of these programs by utilising their grid features. I pick which program I'll use for a given piece/asset based on what I need to do.

I personally use Aseprite, Pyxel Edit, and Photoshop, as I find each has their own strengths, and all three have similar UIs, just adapted for different things. Other popular pixel art editors are Aseprite (possibly the best for pixel art animation, good but not great at everything else), GrafX2 (good-to-great features for all kinds of pixel art, but the old-school UI means a steep learning curve if you're used to modern art programs), and Pyxel Edit (great features for tiles, good for animation, decent at everything else).

I haven't used Pro Motion NG myself, so I can't tell you anything specific about it. You can make pixel art in Krita, but it has no specialised tools or Quality-of-Life features made for it, so if you only want to make pixel art, you should obviously go for a program designed for it!

Krita pixel art