In a nutshell, since the new "update", does Advanced Scouting have any effect on projections seen as far as Amateur Draft prospects are concerned? If I'm maxed out on HS and College scouting will I get accurate readings even if my Adv Scouting is at "0"?

Advanced scouting does not, and never has, had any effect on projections seen for amateur draft or IFA prospects.

Advanced scouting ONLY comes into play on those prospects after they have been drafted and signed.

Even "maxed out" scouting budgets will never give you completely accurate projections.  Since the update earlier this year, maxed out COL, HS and IFA budgets will be less accurate then they were previously.