I'm so glad you've done this test, I been wondering about these (and Fimo) for a long time.
I've tried all 3 of those but like you, not the Fimo Deko Gel.
I'd really like to try the Fimo, as I think it is pretty clear even at low temps, or at least temps as low as Premo clay bakes at.
I wasn't sure how clear Kato would be at 275C, since I've used it to make clear beads, but I used a heat gun not the oven.
I've only used TLS and Bake and Bond to fix breaks in baked clay, or to ensure a good bond between raw clays, like when putting 2 different coloured clays together, yet not blending the colours - funny, I never thought of bake n bond as a clear liquid clay, just as a sort of clay glue. I use them interchangeably, whichever is nearest to hand - does it make any difference, which one you use?
Not sure what you meant by sanding the Bake N Bond, does it get clearer if you sand it? Or did you like it when sanded for some other reason?
You said it will buff up quite well... in what way 'well'? (Does TLS do the same?)
Please, please, do try and do the Fimo as well, that would really complete things for me.
As usual a very useful and informative video. Thanks for doing this.