im a white tshirt lover. 90% of my tshirts are plain white tshirt. bases on experience, i would recommend Gildan (cheap but quality is great) or, if u prefer abit on the modern cut, i would recommend burton london menswear, surprisingly they make decent quality plain white thirts with modern cuts.

i usually wear airism from uniqlo on the inside, and wash the white tshirts seperately form others. and hand dry instead of using dryer to maintain the shape.