(1) How long was eCS working after you installed it that way? Was that a system image or sector-by-sector clone? I'm unsure the former gets the Boot Sector & MBR. Was it a clone of the entire HDD including the Win 10 partitions? Or how/when was Win 10 installed?
(2) Questions arising from those threads & article I posted...
(a) Did you install new hardware like ilounge & SasaSamardzic were doing?
(b) Was the hardware the same on the old & new computer?
(c) Did you disable/enable any hardware in BIOS?
(d) Did you change BIOS settings like ACPI or AHCI?
(e) Did you resize or move partitions?
(3) Well, a normal Legacy install has 3 partitions: System Reserved, Windows, & Recovery. Then, System Reserved gets the boot files & BCD. Recovery gets WinRE.wim. But it's possible for the Windows partition to take on the role of each of the other partitions. Then the files all will be on C instead.
(4) In a UEFI install, the BCD gets a Firmware Boot Manager, seen this way...
C:\WINDOWS\system32>bcdedit /enum {fwbootmgr}
Firmware Boot Manager
identifier {fwbootmgr}
displayorder {bootmgr}
{140ab3f9-3491-11e7-a4a0-952787f57a8e}
{140ab3fa-3491-11e7-a4a0-952787f57a8e}
timeout 1
It's a means of communication between Windows & BIOS. It shows the state of the BIOS boot screen & can be used to change it.