So, i have two questions

Question 1: Alternate Tuning

about alternate tunings such as Andy Mckee and Antoine Dufour and others from Candyrat.com now this may sound stupid, (bear with me im new to this acoustic thing ) but do they use different sized strings or different strings at all to get so low and keep tension? or do they just have some strings way more loose than others?

Question 2: the Slapping

Is there anywhere that i could learn about this? what exactly is he doing? slapping the fret to get a quick sound of that fret? or is it like a slap to get the tap sound. If someone here knows how to do this (which im pretty sure someone can) can you give me an explination or give me a link or reference where i could visit to learn more about it, i would greatly appreciate it
Question 1: It's really up to you, you can do it either way, if you're going to specialise in lower tunings buy some thicker strings, as well as mix and match different strings.

Question 2: Can't really help you much, I just assume it's like a bass slap.
Alright thanks, i thought it was liek a bass slap, but when i do it it doesn`t work out so well, but it must just require more precision than a bass, cause i can do it on a bass.
First, I must recommend that you look into Michael Hedges' music.

As for your first question, usually playing in alternate tunings will result in there being different amounts of tension across different strings. Since most alternate tunings involve lowering the pitch of open strings, heavier guages (.012s minimum) tend to be preferred. Since most guitarists who use alternate tunings tend to change which alternate tuning they're in often, it makes little sense alot of the time to try to precisely match tensions for any particular tuning, unless you use that tuning almost exclusively on the guitar in question (which may be the case with some of the more common tunings, like DADGAD or open E).

As for the slapping, I'm afraid I'm not sure which kind of "slap" you're referring to. It's common in modern fingerstyle to strike the strings at a harmonic node to create a bell like effect (a "slap" with the flesh of the fingers), it's also common to slap when not at a harmonic node to set the strings ringing. Tapping is obviously very common, but I can't see it being referred to as a "slap." You could also be talking about the "slap" with the side of the thumb that has been inherent in fingerstyle for decades, which gives a percussive effect, often used by John Martyn among others.

Also, don't neglect finger picking and strumming techniques.
My name is Tom, feel free to use it.
Thanks for the answer, so for the slapping i mean the ¨slapping¨ of the strings that they use for the flesh, i`ve seen andy do it alot hope you can help me learn how to do it cause it doesn`t happen anything like his when i try it