Mixing brands in the same drawer
Short answer: It works fine as long as you keep track of which size belongs to which brand. Write it down once and you never have to guess.
The advantage of mixing
You can pick the best from each brand: one for everyday, one for training and one for days when you want something closer fitting. No brand is best at everything.
The drawback
The sizes do not run together. A medium from one brand and a medium from another can be two centimetres apart in hip width. See bamboo underwear for men.
How to keep track
Write the brand and size in the notes on your phone. Then a reorder takes thirty seconds instead of half an hour. See JBS of Denmark and Boody.
Frequently asked questions
Do different brands wear differently
Yes. A heavier fabric lasts longer than a light one, whatever the name.
Can you wash them together
Yes, if the fabric type and colour go together.
Does the drawer get messy
Not if you sort by type rather than by brand.