Best to block autostart apps, or let them run at boot time? When Android was still a baby green robot, I would go through all user-installed apps (not system apps), and turn off autostart privileges on most of them.  This would make the Android device boot much faster and start with more available memory.

Then I started wondering: What if some of those apps are actually doing something important when the phone starts?  Perhaps they are cleaning up their temp files, compressing databases, sorting indexes, or performing other important maintenance or initialization tasks.

Without reading the source code for each app to see what it does at boot time, I decided it was better to leave them alone and let them run on bootup.

Now, as Android devices have gotten more storage and hold more apps, I've begun to rethink that logic.  I've seen Android devices with over 75 apps running at bootup.

What's the best practice now: Allow most user-installed apps to run at boot (if they are set to do so), or block most of them?

Stability of the operating system and apps is very important.
-As you know there are the custom apps which you download from the external source(play store etc) and the standard android apps which come inbuit in the Android OS(You might/ will also have some bloatware)

-Now as you disable the custom apps which you download you will get the desired result of free RAM,faster loading,less battery consumption.

-But if you disable the standard android apps then definitely you will have issues with the device to run normally.(i.e if you close/stop a standard app  then your data transfer may not get enabled at all etc).

-So you can go ahead with closing/stopping auto restart custom apps downloaded from the external source but in some apps its hard coded to auto-start by default i.e even after stopping its auto start it will restart on its own as per the Android architecture so to some extent you will get relief from RAM management.

Note:-Although the Android devices are featuring with more chip level storage their Operating System Size has also increased manifold.That is in order to support an Android Kit-Kat v4.4 operating system on your device it should have a min 2-3Gb of on board storage space apart from the space for Custom android apps downloaded from external source(approx value depends on the device and the amount of bloatware present)