If a dvt is in the peroneal veins, is it less dangerous because it is distal? or is it still dangerous? does it matter how big the blood clot is?

Still serious: Depends on size of the individual peroneal veins, which are generally small but when dilated with clots can be larger. The clots can be long and of variable diameters. Propagation is a problem and requires full therapy.

Always a concern: Anticoagulation is advised, although some would follow with ultrasound when DVT in tibial veins are provoked (have a reason like recent surgery, on bcp). Tibial vein DVT (which one might consider to be distal and clot burden small) can result in pulmonary embolism, so one needs to see a doctor, obtain appropriate venous ultrasound study of both legs, and have followup.

Peroneal: this is still a dvt and should be treated with anticoagulants though the risk of dvt is less due to smaller size blood vessel which makes the clot size smaller