Can you tell me what size of artboard should I use in Illustrator and also what kind of settings should i do like CMYK vs. RGB while making a logo.
Going to use this for print mostly, but also digital.
To be blunt: it's irrelevant. As you can always change artboard size and colour settings later, and scale your logo infinitely, just choose whatever you like.
If your logo is going to be printed (read: if you aren't completely sure that the logo is going to be used on-screen exclusively), it is very wise to do the design of the colour palette in a CMYK environment. That way, you are sure that you always pick colours that are printable in an affordable way. You could, however, still design the logo shape in a different colour mode if that suits your fancy.
There are corner cases imaginable where a very small (a few centimeters) or a very big artboard size (meters) would give you problems later. Those are, indeed, corner cases like when you use pixel effects. Most of these cases are solvable by scaling your artwork.
tl;dr: it doesn't matter. If it ever comes into play, you can easily fix it.