I'm not an expert, I'm sure someone more knowledgeable will chime in, but...
"why do I see in some post about people with a 2-2.5" kit in the front and a 1.5" kit in the rear? "
I believe some people lift the rear a little as well so that there is still a little rake, that or if the 2-2.5" up front ends up being too high, they need to compensate to keep it level. I've never leveled a truck, so I'm likely not the best responder, but it seems logical to me those would be good reasons why.
"I'm looking at getting a set of 295/65/20's but don't want too much of a lift. Also would like to keep the factory rims."
With factory rims and no spacers, 285/65/20's will fit, but 295's are almost a 1/2" wider. If it ended up being too tight, you could always throw a spacer on there, they aren't terribly expensive, but IMO spacers are not a good idea. Then again, as much as some of them look really nice, I do not believe in any rims offsets that do not match factory, but I have a good reason.
"Would a 3" lift just be as cheap and easy instead of a leveling kit? Also my truck is a 2006 Quad."
Lift kits cost more than leveling kits. Both lifts and leveling kits generally seem to level the truck as far as I know. I think leveling kits are a bad idea if you ever plan on using your truck as a truck. Just my 2 cents.