[SCOTI]

You will do well well as a beginner using Ride Techs products.
Drop spindles do help get 'more' drop w/o affecting geometry.

How low w/o removing the inner fenders is subjective. Some guys are ok w/running really short OD tires & thus have no need to remove or alter the inner fender wells because there's no rubbing while others run normal (original height) or taller tires & can experience rubbing. A safe bet is a 5/7 drop w/original height tires. Once you go beyond that point, things start getting cramped.

The c-notches are typically required for anything beyond 5-6" rear drop... especially if you'd still like to use your truck as a truck (seems silly not to).

For the suspension geometry of the 63-87 GM truck platform, bags can help w/ride quality on aggressive drops. Mild drops would be a wash....