For deciding the SEPM 12.1.6 clients to install Standard or Reduced size client

Dear Sir,

We have upgraded the SEPM from 12.1.3 to 12.1.6 recently.

SEPM 12.1.6 let us to choose standard size and reduced size client installation.

What is the difference for these 2 version clients except size?

Is it ok to deploy all reduced size to whole company's PC Clients? Will it cause any security issue?  

How can i specific some clients install reduced size, and some install standard size?

Once i want to change the reduced size client to standard size, is it necessary to uninstall the old one before install?

thanks