Hi sb,
There is more about the different types of mattress protectors and the tradeoffs involved with each type in post #89 here.
The Dormio mattress protector you are considering looks the same as the St Dormeir and may just be a rebranded version. It would certainly make a good choice if “water resistant” is OK with you and it would be more breathable and would have less effect on sleeping temperature than a protector that has a waterproof but “semi breathable” membrane.
Phoenix