Not with standing the usual problems of different countrys rules and company SOP's
In the UK I have never done any line training without punters in the back.
My training went
ground school
sim (tri/tre)
License skills test (LST) which also includes an Operators profiency check (OPC) (TRE)
Base training/ check which is the 6 circuits. Some do fail the check and have to go back to the sim then more circuits. (TRE)
Rating issue
Then the next flight was done with punters by a training captain (CRMI).
Then after xx sectors after packing up for the day. You get a quick handshake and let loose with normal crew. This is your first Line check
Line checks can only be carried out by CRMI holders ie Training captains. It can be either sitting next to you or the training captain can sit in the jump seat and do 2 at once.
OPC can be carried out by a TRI/TRE every 6 months depending which CAA rule book you look at.
LPC by a TRE max 12 months but you can do it earlier up to 3 months but it screws it up for the timing of the OPC depending what rule book your using. So most combine the LPC/OPC.
Highlow it really isn't something to worry about. You will be pushed through the required hoop's. Each company is slightly different. In the UK there are 2 different rule books depending if you have a CAA AOC or a JAR AOC. Some of the rule differences are quite small and others are quite marked.