Measurements - a real beginner question

[PhilipHerlihy]

I'm just starting out again on a remodelling project which had to be shelved some years ago.  I've upgraded from HD Interiors 2014 to HD Architectural 2020.  I'm also tinkering with Room Planner.

 

The first thing I need to do is get an accurate set of reference measurements!

I've invested in a Bluetooth laser measure (Leica Disto D2 - works well), and I've tried out three apps with it.

1. ImageMeter Pro (under £4) works really well - it's quick and easy to annotate photos of the site with measurements.
2. Leica Disto Plan (free for what I need).  The "Sketch on Photo" facility works well (though I prefer ImageMeter).  Problem:  I've tried the "Sketch Plan" facility and I found it a real struggle to achieve the definitive "reference" set of measurements I want to be able to return to.  Every measurement I input seems to change others already entered.  That's after several attempts at my first room!  I did have "snapping" turned on, but that seemed to make it worse.  Without snapping, drawing a passable shape, then entering the measurements produces a recognisable but crazy version of the initial sketch (as the app tries to draw it to scale) but without the assumption that walls which were initially sketched at 90° to each other have to stay that way!  At least the figures stay as entered - I've become fearful of relying on measurements which were actually changed by the app's idiosyncracies.
3. Room Planner.  Very impressive, though it takes a while to figure out how to do things with a very limited set of "adjustments".  Again, I felt I had to battle with the app as changing one measurement led to unwanted changes in others already entered.  As I got more familiar with how to use it, I found I could get a room approximately right - but what I want is a room that's exactly right. More disturbingly, when imported into Home Designer, the figures aren't exactly what I entered in Room Designer - though this may be due to HD being more picky about precisely which part of a wall's structure you're referring to.
   
   What I want is a set of accurate measurements I can come back to if/when I need to.  It seems to me that for all the attractiveness of creating a scale drawing right there on my mobile, I may be better off simply with annotated photos, and that brings me back to ImageMeter.
   
   Question:  Am I missing something!  Advice from old hands (and young ones) warmly appreciated.