Water filters? Hand sanitising gel? FFS you are talking about the wettest, cleanest place in Britain here! Just wash in the burn and drink it and you’ll be fine.
Nobody has really mentioned the biggest issue when camping in Scotland – MIDGES. Take a DEET repellent, some mossie coils to burn upwind of the tent when you’ve got to have the flap open, a small can of insecticide for spraying the tent before you close the zip, a head torch and a big fat book to read while locked in your tent as the Caledonian Luftwaffe are marauding outside, and an old plastic pee bottle so you don’t need to go outside, which means opening the flap and admitting more midges.
Try to pitch somewhere high up with a decent breeze and keep away from damp, still, shady places.
This advice is from one who has aborted quite a few Scottish camping holidays just because of the midges.