I have an Aldi roll top dry bag, it's OK. Thinner than the Ortlieb, and the fastening is a bit crude, but OK. It seldom leaves the house though. I favour plastic bags for keeping stuff dry IN my rucsac/panniers, as they are cheap and you know where they are at the appropriate packing moment.
I don't sweat the tent getting wet, it's a tent. It gets aired when it is pitched or arrives home.
There's nothing wrong with a pop up tent, I used one last weekend and it was great. I bet I spend more nights in it than *proper* tents. Horses for courses.
If you arrive in the car at 11pm and you can have a superduper tent in 20 minutes or the pop up *now*, have a guess. I'm in bed before most of my pals have got their sleeping bags unrolled.