Yes, it will effect the page load time but not to that great extent that it will start affecting the user experience. If you optimize the website for speed then the effect of additional slider can be offset. I suggest you to take a look at our performance optimisation guide for more information:
You are referring to the first slider or slider under a specific slide? I suggest you to take a look at following resource for some inputs:
Yes. How much it will affect the performance of the page depends on how many layers your slide contains and the type and number of effects applied to the layers and the slider. We have no documentation on this though and it’s also best that you monitor your page’s performance when you add anything in the page or slide.
Regretfully, there’s no option for this. This could be possible with custom development but this is beyond the scope of our product support.