accept vs return in mangle

RouterOS Beginner Basics
1

Hi,

as the first rule in my prerouting chain I have this:

/ip firewall mangle

add action=return chain=prerouting comment="established no-mark" \
    connection-mark=no-mark connection-state=established

It is to save CPU by not processing next rules if connection was established and there is no connection-mark.
The question is - is there any difference between the example above and that rule:

/ip firewall mangle

add action=accept chain=prerouting comment="established no-mark" \
    connection-mark=no-mark connection-state=established

?

2

action=return is supposed to be used with custom chains - to return the packet to the original chain it came from (using the jump action).

I am actually not sure what action=return does in one of the built-in chains.
Documentation doesn’t specify it either.

If you want it to be not processed anymore, use action=accept.

3

I’m guessing that as there is no further rule to “reject” the packet, it will perform default “accept”