Setting the conduit out at the trunking is done to help drill in-situ trunking and to help do up the bush inside.  I prefer not to set it to be honest.

You may find you need to set conduit a touch at some accessories - not all have their knockouts at spacerbar saddle depth.

I have found with rotary isolators it is easier to use 'hospital' saddles which stand off the wall a tad more.  No setting required.

You could opt for galv trunking at waist height, and just use a conduit coupler and two bushes at accesories.  This is quite often preferred these days - easier to install and maintain.  Have a look at Phils garage in Eastenders  

You could also use galv trunking and PVC conduit.  Nothing wrong with this in a lighter commercial application.

With steel conduit, you will require a 20mm pipe bender (hired or bought), and a stock and die set to cut the threads on the ends.  With PVC conduit, everything is cut and (ideally) glued, although just push fitting is fine for inside use.

You can drill enclosures where you wish, although I would be looking to use metal clad boards if it was me, particularly type A boards, such as the MEM or Merlin ones.  That would be my preference.