You can use all of them! In slightly different ways. If you're looking for a coursebook, Outcomes Upper Intermediate has a good section on vague language like this in unit 15. So so (I usually use this when someone asks me how I'm feeling and I'm not feeling very good. I'll shake my hand and say so so. It means "not bad" or "ok". I usually only use it when I'm not ok but I don't want to say something negative) More or less (usually I use this when replying to other peoples closed questions. "Do I need 500g of pasta?" "Yeah, more or less" and it means approximately. Another great phrase for this is "give or take" Ish (not ich! You can add this to a time to say it's a approximate, for example "I'll meet you at 12.30ish" = about 12.30, but not exact. You can also add it to an adjective like "It's a greyish blue colour" = it's a bit grey and a bit blue

They are different in meaning. "So-so" is a description of how good something was. "How is the coffee at Dunkin' Donuts?" "It's all right. I'm not crazy about it. It's so-so." "More or less" is a way of saying that your statement is not precise. "How long does it take to drive to New York?" "Five hours, more or less. It depends on the traffic." "How is the coffee at Dunkin' Donuts?" You cannot answer this by saying "more or less. "How long does it take to drive to New York?" You cannot answer this by saying "so-so." "How much does coffee at Dunkin' Donuts cost?" You could answer this by saying "Two dollars, more or less." "I'm driving to New York. How good is highway I95?" You could answer this question by saying "It's so-so."

thanks

“More or less” is generally more common than “so so”. But they have different usages which is a little difficult to explain. “So so” would be used in place of “okay, fine”, but “more or less” is essentially something like “yes”, but with a little element of doubt. “Ich” is not an English word.