Trusted brand. 10w power. https://uk.anker.com/collections/wireless-equipment/products/a2524-1
Don't need mental fast like 25w on a pad charger in my experience.
I've used wireless chargers for years.
Only for cable charging mate. The wireless stand should come with the correct adapter. An s8 is an older phone now though so don't expect miracles.
I have a flat rav power charger wireless at work. Was like a tenner and is 3 years old. Still works for top ups.