Remote Tag Provider vs Standard Tag Provider

Hi,
What is the difference between Remote Tag Provider and Standard Tag Provider, are there any functions that I can't implement with a Remote Tag Provider and for the ignition license as I have to manage this I imagine that I must have two licenses or total 4 gateway with redandancy ?
For redandancy also if I have two redanded ignition servers what is the limit if I use a Remote Tag Provider ?

The difference is that a Remote Tag Provider does not establish any communications to any devices or other information, except to point at the source tag provider. Standard Tag Providers perform all OPC subscription, reference/derived/expression tag operations, and execute all tag scripting.

They are not interchangeable at all.

Both kinds of tag provider are part of the platform license of Ignition. (Redundant backup gateways need their own, discounted, licenses.)