YECs, how do you explain meandering canyons?

Sorry, if that had happened we would see much more extreme erosion on the outside of the bends, since the rushing water would exert enormous force on the outside walls as the water changed direction suddently. We don't see that. Your scenario is falsified. By following the template of the pre-existing shallow meanders. This is called "incised meanders". Well-known phenomenon, observed in many places in various stages.

Any fluid dynamics textbook.

Not much merit. Water flows downhill. Slow moving water on a near-flat plain produces meanders. A "backwards tilt" and fast-moving water might produce changes in direction (which would be accompanied by severe undercuts and erosion, which we don't see, on the outside of the direction changes) but it wouldn't produce the back-and-forth pattern of meanders, nor would it produce 180^o changes in direction in a short distance

All of science is the best explanation that fits the known evidence. The best explantion for the Grand Canyon that fits the available evidence is that the Colorado River carved it; this is so well established that we might as well call it an established fact. Of course, it could have been sculpted by incredibly powerful three-headed polka-dotted alien beings, and that fits the evidence as well, but nobody takes it seriously. No hypothesis about the Grand Canyon is worth considering unless it explains something that "carved by the Colorado River" does not and explains absolutely everything that "Carved by the COlorado River" does at elast as well.

This isn't really my area of expertise, but ...I don't know of any features the the CBTCR {grin} model does not explain. Many creationists don't much like the fact that the CBTCR model rquires that the Colorado Plateau be uplifted slowly, by plate tectonic processes, as the canyon is being carved. That is, the top of the canyon is crrently above the headwaters of the Colorado. Not everyone agrees about some details or the exact timing, but there's no serious contendor for an alternate theory. The flood-runoff theory is a non-starter, even given the lack of evidence of the existence of such a flood at all. The near-vertical walls of the Grqand Canyon show that it was carved slowly while the rock was lithified (that is, hard), unlike the approximately 45 degree walls of the "Grand Canyon of the Toutle River" (carved by runoff after the Mt. St. Helens eruption, and often cited by creationists as "proof" that the Grand Canyon could have been carved quickly). See the pictures at the end of Young-Earth Creationism and the Geology of the Grand Canyon: Part 2: The Grand Canyon. (Also the amount of material removed at the Toutle Rive is hundreds of thousands of times less than the amount of material removed to form the Grand Canyon). The pattern of the Grand Canyon and the Colorado River basin, with branched side-channels and several 180-degree turns, is totally unlike the pattern of flood runoff seen in the Channeled Scablands. Events in the Vicinity of the Grand Canyon of the Colorado River and Evolution of the Colorado River and its Tributaries, including Formation of the Grand Canyon: Geologic History of the Grand Canyon present the mainstream theory pretty well.