Dithering has zero effect on sample rate conversion. Dithering when converting sample rates won’t really hurt your tape, but it will add time to the bounce/render when you apply it.
In theory, you want to dither whenever you change bit depth. It helps to mask strange distortions during fade ins/outs, and it technically masks some (usually imperceptible) artifacts when volume is very low. In practice for taping, it doesn’t make a huge difference whether you dither or not. I always dither when going from 24 to 16 bits, if you’re going from 32 float to 24 I’m skeptical anyone would hear the difference between dithered and not dithered.
A good exercise is to try bouncing two files from 32 to 24 bit - one dithered, one not dithered. Especially on fade ins/outs. See if you hear a difference. When I was younger and my hearing tested up to 23k, I could hear it but decided even back then it was a subtle thing that I’d do for polish but wouldn’t stress if I forgot to add in; these days with my hearing only going up to 17k I’m not convinced I could hear it.