However it's done, it's an upgrade
. You obviously cannot upgrade the Win 8.1 product itself by patches, it has to be a fresh install.
When the preview upgrades to a new release it keeps the old version compressed. Using "Disk cleanup" wizard you can then remove the "older version of windows" and it releases about 4GB.
Win8 may not have a recovery partition, as the OS has similar tools built in, depends on the laptop maker.
Yes I would want it booting direct into W10 and ignoring the other, but how much of the disk is released I have my doubts about. Having done several older Win version updates. IIRC most of it stays where it was.
Disk cleanup works better from W7 to 8 etc, than it did from 2000 to XP or XP to Vista - but yes, if you can get a full ISO downloaded, burned to DVD or USB stick, and install from there that is generally more efficient use of disk space. That way however you have to find all your drivers and reinstall software again
plusnet unlimited fibre - 2 Jun 14 - 470m - 80/20 - Summer/dry sync 55/9.4, Winter/wet sync 52/9.1
15 years broadband (1999 ntl:cable trial) - Asus RT-AC68U with HG612 - BQM - Summer PN speed - Winter PN speed