Pants and shoes I try and buy in-store.
I’ve got my go-to brands for shirts and underwear that I know fit well, so I usually just buy a shitload when my old ones are worn out.
Outerwear is 50/50%.
Most online retailers will let you try and return goods. In the EU you can return anything bought online within 2 weeks, no questions asked (by law).
A lot of fast fashion stores might just burn returns, others might sell them at an outlet. And it cuts into they already thin margins. I try to avoid returns.
I remember when I bought my iPhone 3GS back in the day.
The only option was to buy it carrier locked on a one or two year plan in my country. Of course it was exclusive to a carrier that wasn’t my choice of carrier.
I signed up, put it in a drawer and waited for the imminent jailbreak and unlocked modem firmware. It dropped two weeks later. After that one year of payments they unlocked it through official means.