I’m about to build up a new frame that has internal cable routing. I obviously have to route the rear mech cable and rear brake through the frame. So with regards the rear brake which end of the brake hose would be best to pass through the frame. Is it easier to pass the caliper end through or the lever end The brake in question are the new Zee and like other brake have a large nut which would have to be removed which then means new olives etc.
or is it a case that both ends will need dismantling however I go about.

Also any tips I need regards threading all cables through to avoid rattling etc.

There shouldn’t be much difference, you might be able to leave the olive in place if it’ll fit through the frame. It really depends which end is the easier to extract from the frame – i.e. if there is there a small, awkward hole one end and larger hole with good access at the other end then go small to large.

If the routing is the same both sides then try the mech first and find out which way is easier then do the same with the calliper.

If the routing is loose in the frame and you have enough access then try to get some narrow pipe lagging (or similar) into the frame then run the cables through that, if you can’t do that you can use zipties tightened around the cables with the tails left in place to stop the cables rattling in the frame.