If it's still fermenting, still cloudy, then yes, it will taste yeasty, and possibly seem moreso than before for the reasons you suggest. This should lessen as the mead finishes fermenting and clears up as the yeast drop out of suspension.
Sorbate won't stop a fermentation, all it does is make the little yeasties' pizzles fall off so they can't replicate. Most of the time even sulphites won't stop a fermentation if it's still active. If you really want to stop it where it is now, I'd recommend cold-crashing it to force the yeasties to go dormant and settle out, racking off them, and then hit it with sulphites and sorbate.
The difference if you want to add juice in secondary is based on whether you want this juice to ferment or not. If you want it to ferment, go ahead and rack it anytime but you'll have to wait a little longer for the yeast to finish their job and settle out, if you just want it to be the equivalent of adding a fruit juice pack like in a wine kit and have it not ferment, then hit it with the stabilizing chemicals first, let it clear a bit, then rack onto your fruit or juice.
Sorbate won't stop a fermentation, all it does is make the little yeasties' pizzles fall off so they can't replicate. Most of the time even sulphites won't stop a fermentation if it's still active. If you really want to stop it where it is now, I'd recommend cold-crashing it to force the yeasties to go dormant and settle out, racking off them, and then hit it with sulphites and sorbate.
The difference if you want to add juice in secondary is based on whether you want this juice to ferment or not. If you want it to ferment, go ahead and rack it anytime but you'll have to wait a little longer for the yeast to finish their job and settle out, if you just want it to be the equivalent of adding a fruit juice pack like in a wine kit and have it not ferment, then hit it with the stabilizing chemicals first, let it clear a bit, then rack onto your fruit or juice.