I was one of the larger court house steps buyers in our market for years.. and there were folks that would come to the sale and if we bid they bid.. they knew we did our due diligence on title etc.. so they could just short cut it.one particular one was this Dentist wife.. it would irk me.. so I run title on this one.. then do my usual 6 am drive by before the sale to make sure its still standing.. and lo and behold  full of bikers and pit bulls and etc etc..

Short cuts will likely lead to failure. 95% of new investors fail.

All the rules / methods you list are as 'rules of thumb', 'short cuts', etc. just as you can guesstimate a roof re-shingle just by the sq footage without selecting material, taking in account specific damage or getting quotes.Using any one of these methods is just a time saver to see if you should invest the most precious thing you have - Time.

You may be able to slide by, but as you build your portfolio all the shortcuts taken add to the collective risk.  

Don't take the shortcut (lazy) methods.

Turnkey investing or going the roofstock route is definitely a shortcut way to get started, but again, depending on your time horizon, I think self-education is important, so once you pick a market, visit it (excuse for a little family vacation), meet realtors and contractors, attend a local REIA meeting to make local investor contacts (they are very easy to find via google search or on meetup), see some properties, and become a more informed investor. 

Agree with @Matthew Paul My favorite brush is the Wooster Shortcut. 

In real estate investing, there is no substitute for doing your own due diligence and there are no short cuts.

That being said, I also know that there are definitely things that you never want to short cut. 

Note investing is not a shortcut to get rich overnight.