FS slappy, no comply tailslide can look OK on curbs and might help with a piece of the puzzle. Taking a no comply straight to tailslide on a curb or ledge will be awkward. Try it on a bank first.
This is correct, slappy is easier and works on ledges too because then you can guide the board up the wall and into the position with that back foot (just don't stand on the front foot as you're doing it since one quick hop is the very principle of the trick). Popping and jumping towards the ledge is harder unless you have good straight step hop technique where you can really level them out, otherwise it's a bit awkward to control the pop, angle and then the actual tailslide with just your back foot. That's why 270'ing into them is easier (or doing the trick to tail on banks/coping) because then you're just swinging the back of the board in front of you and have clearer control of both timing and momentum.
Or I reckon going over the top of the ledge at first as opposed to parallel (just like how some people 'cheat' nosebluntslides) may be a good first step, that's the approach I remember taking to learn no-comply lipslides and it worked out for me (still feels super awkward though).