Just a personal opinion but I would add footnotes to #3 and 5
#3, pop can (aluminum / shim) of course can be added. I've done it myself. But recognize you are somewhat kind of defeating the purpose of a collet which is minimizing the number of contact surfaces for both accuracy & grip. Here you have gone from 2 surfaces (collet to part) to 4. If you are just turning something that has to be gripped then who cares. But if you are counting on concentricity and need to work sub-thou, this is not optimal. Unfortunately, the solution costs money. Either a finer graduated collet set like 1/64 vs 1/32 on IMP 5C for example. Or ER's which span a wider range per collet but have other potential disadvantages depending on the application. BTW I use (I think its called flashing?) tape which is kind of a aluminum foil with adhesive back. You can wrap it over a part surface beforehand & it stays put going into the collet or chuck which is less fiddly than shims. Mostly I use it to prevent bite barks but it can buffer annular distance too.
#5 'better' is of course relative. Consider a very ordinary operation - a threaded hole: 1) drill a pilot hole 2) tap the hole 3) counterbore or chamfer the hole = potentially 3 collet changes depending on respective shank diameters. Potentially 4 changes if you had to insert a positioning indicator as step 0.5. That consumes a lot more shop time than opening & closing a drill chuck, especially a keyless one. Now multiply that by the number of holes. Is it more accurate? Depends on the relative quality of your chuck, your collet & position of tailstock. Holding EM's is debatable. I use collets all the time for small ones especially swapping metric & imperial. But there is a reason for Weldon style shanks (a ground detent) even on 1/4" shanks, but especially on bigger tools. Its a form of key to prevent spin-out and also pull-out under load. An R8 collet for example requires torque via the drawbar transferred through the taper seat for tool clamping pressure. I wouldn't consider it excessive wear & tear on a hearty mill in lighter loads, but my point is a dedicated R8 end mill holder confines gripping gronk to the holder itself. The business end of the spindle just has to hold the tool holder. Again, just an opinion, lots of ways todo machining.