"Sometimes,instead of cutting,ill just sit and pull out my hair one strand at a time"

... therefore it is a replacement of cutting.

If you're doing it for the pain or hurting yourself for comfort I'd say it is SI.

Chewing on hair I would say is more nervous habit [not SI since you arn't really injuring yourself (at least not from what I can tell)].

And does it matter, I'd say yes if it hurts you or others around you... by my definition, 'hurts' also includes feelings.... so if it makes you or others upset, mad, disappointed, or brings feelings of shame and/or guilt I would say it is a bad thing and you should work on developing better coping mechanisms.

I hope I answered your question.

Good Luck