Blueprints / custom nodes

Can i make any custom node if i know c++ well or there is limits to what node can i do
And is blueprints limits the same as c++ ? Or it is just used in prototyping

Are blueprints used just for prototyping ?

Making function nodes is very easy, you just add BlueprintCallable and BlueprintPure specifiers UFUNCTION and also add Category=Something specifier and C++ function turn magically in to blueprint node, here you got tutorial:

Note: you don’t need to use FriendlyName and CompactNodeTitle so obsessively as this tutorial use, UHT will pick name of function

The limits is what reflection system supports, most notably there only 2 integer types supported int32 and uint8

No you can build a full game using Blueprints only. Blueprint is a complete scripting system for Unreal Engine 4.

But many developers use Blueprints for prototyping only and convert the BPs into C++ classes eventually. But that is needed only if you are concerned about performance or if BPs does not allow you to what you want.