That's good intarsia, @MyrtleLion .
I don't think it matters which yarn goes on top and which underneath, although people do advise putting the new yarn on top.
Try watching Debbie Abrahams here or from about 4 minutes 30 seconds.
It does matter in stranded knitting/fairisle, but again "Freddie on a galloping horse" wouldn't be able to tell - sorry, this is a knitter's way of saying small mistakes won't show, or it won't make that much difference.
From the video I learned, when you've knitted the first stitch in a new colour, stop and pull separately on both yarns to tighten the stitches.
You are being good to cut your ends and weave them in as you go. If I'm going to use them again a few rows later in approximately the same place I just carry them up - see here or for that. The video shows the yarns being carried up the edge of the work but it's the same method if it's at a border.
If I'm doing a 3 row stripe, so the yarn would be at the opposite edge, I change the pattern and do a 2 or 4 row stripe.
(I can't add anything about ancestry, and can only get on MN after about 10:30pm at the moment, so I'm going back to something I do know a little about.)