I use furled leaders when I'm fishing for bass, both largemouth and smallmouth. Yes, I use a tippet with it. Normally 5 to 6 feet of fluorocarbon, ranging from 12 to 25 lb test. The leaders, I have three or four of them are made from thread. They are 4 to 6 feet long. I didn't make them. I swapped materials and flies for them with someone on one of the boards I'm on. Might have been this one. I treat them with floatant. I prefer fishing top water for bass, so I do use a WFF line with them. Depending on the situation, I'll use other lines. I have two spare spools for my 6 wgt. One has an intermediate sinking line and the other a sink tip line. With the intermediate line, I use a hand twisted fluorocarbon leader, 5 feet long plus 5 feet of tippet. With the sinking line I use a 5 to 7 foot piece of fluorocarbon as the "leader", no tippet.
All my connections are loop to loop. All my fly lines have loops on the end of them. The furled and twisted leaders have loops at both ends. A loop to loop connection of fly line to leader, and then a loop to loop connection of leader to tippet. If I'm using just a straight piece of fluorocarbon, a loop to loop connection to the fly line. A bit complicated.
To answer your last question. Not all bass lines are floating. What line you use is situational and preferential. Unlike, Mike, I'm willing to use a sinking line, but it's situational. The only time I really do that is on a lake I go to in Northern Ontario where I cast to shore structure around islands and rock piles, but the water drops off quickly to 10 or 15 feet.