GhenghisKahn

Dont have only experience with that particular brand, but they look water-resistant not waterproof. Cordura probably. Yes, the internal lining looks to be plastic of some sort which is technically waterproof, I suppose.

Have had similar panniers with a lid like the ones about which you're asking. What I did was make a mixture of clear silicon caulk and white or mineral spirits. Don't use turpentine. Trust me. Half and half. Remove any external or internal hardware. Then coat them liberally inside and out with a 3" China bristle brush. But any quality oil brush will do. 2 on the inside and 3 outside. Allow each coat to dry thoroughly. A full 24 hours. Then when you've completed the coating process reassemble and coat all the hardware 3x as well. This will give you a seamless seal. Yeah, I know. It's a labor intensive process.

Even with all that it's still best to use a kitchen sized plastic trash bag in each pannier as well. Water just has a way of finding it's way in. Especially if you get caught in a downpour. If you're carrying any electronic devices wrap them separately in addition.

Or you can spring for a set of Ortlieb Bikepackers. Which is what I ended up doing finally. Got a set of front bags and used them on the rear. Ortlieb got wind of people doing this for commuting/light utility or weekend treks and rebranded the front bags as 'sport panniers'. Same thing, though. Don't get Roller Classics. They're too fiddley and a pita for utility/commuting/day treks. Bikepackers, though more money are much more user friendly. But, even with Ortliebs I still used a kitchen trash bag in each pannier, too.

But, if you don't commute in bad weather then those you linked will be perfectly fine. But wrap your devices anyway. My background is touring/commuting/utility and trekking, so overkill is my default mode. Probably, no DEFINITELY more than a bit anal when it comes to water in my panniers. Riding 3 straight days in rainy weather will do that to you. Cheers.