I can't tell you the neck routing depth exactly, as it will depend on the neck dimensions and the guitar body, but for a bolt-on you are looking at around 20mm, and a set-neck probably double that.
A bolt-on G neck is pretty similar in ease/difficulty to a Fender-style neck if you go with a flat-top body. The neck will sit quite high from the body to give you the necessary clearance over pickups, and a Fender style bridge is better than a T-O-M style one, just because it's lower. If you go for a LP style carved top, then the neck will need to be angled to get clearance over the top. Which either means angling the neck pocket or putting an angle on the base of the neck heel. Not much, about 3°, which you could do with a wedge placed underneath the routing template. The T-O-M style bridge works better here because it's taller.
A set-neck pocket is harder to rout, partly because it's deeper, and partly because a lot of set-necks are shaped with a slight wedge-shape/fine dovetail to the sides, which helps lock them in place. But this is neck specific. It is always possible to rout the neck sides parallel and use a parallel rout for the pocket. Or else you can trace the heel shame and rout out to match.
A set-neck may also have some angle built into it. On some guitar kits this angle may be built into the pocket, on others into the neck. Even with a flat-topped guitar, some neck angle is a good idea, as the neck will be made to sit lower to the surface, so the angle gives you string clearance over the pickups. So depending on the neck, you may also have to build in some angle to the bottom of the pocket.