It's true that CF reels have inferior drags, if any. But consider what you expect to be catching. If you see yourself catching bags of small to medium size roach, dace and chublets - staples of a lot of river floatfishing - the drag won't really be an issue. I regularly use a CF for that type of fishing on local rivers, and can't remember feeling deprived by lack of a finely calibrated drag. There are places where big fish like chub and barbel are likely to gatecrash, but these are rare even on the Trent and Derwent stretches I fish, and I wouldn't gear up for a once in a blue moon eventuality. A bit of backwinding has taken care of anything unexpected I've hooked this year.
If you're new to river floatfishing, there is one big advantage CF's have, which hasn't been mentioned so far. The second after you've dropped your finger onto the spool/face and struck a bite works differently on the different reels. On an open-face reel, you have to flip over the bail arm, hopefully without giving an inch of slack or fumbling the job. That becomes second nature, but is one extra complication when you're learning the whole thing. On a CF, a turn, or half-turn of the handle, puts the winding pin(s) in play, and the whole thing is foolproof.
There's no doubt open-face reels are superior for versatility and playing big fish, and these are what I use most, but in it's proper place, the CF is a treat to use and its simplicity a virtue.