Odd. I was using VBox 5.0.0, when I tried Win 10 (Pro 64 bit). I had no problems, so I didn't do any extensive testing with VBox, but it was used more than once. Win 10 was causing enough problems without worrying about that (VBox was one of the few things that actually worked properly). Since then, I went back to Win 7 (10 was ridiculous), and I have updated to VBox 5.0.8. Still no problems.
I use nothing except JFS, and I am using AHCI for the drives. The setup is almost identical to what I use in a real machine:
C: is a 2 GB JFS boot drive (eCS 2.1, with fixes).
M: is a 2 GB JFS boot drive (eCS 2.2 b2 with fixes).
W: is my program/data drive. 25 GB JFS advanced.
Each drive is in it's own VDI, so I can attach, or remove, them as I please, or I can attach an additional drive. As with a real machine, I select the boot drive with Air Boot, after starting the virtual machine.
When I install eCS, I do NOT use the Virtual option. That seems to cause trouble (I don't remember exactly why). The Modern with ACPI option seems to work best. You do need to change the default setup so that VBox presents a more modern machine to the software. Also, DO NOT try to use more than one processor in VBox. That seems to cause problems too, although I haven't seen what you see. Mostly it just stops running, requiring a reset (that may be fixed, I haven't tried recently).
I have also used the Export Appliance thing, then Import on another host (including a Linux Mint host), so I get exactly the same setup (except it is smart enough to change the MAC address that is created for the NIC). I also need to change the machine name, so I don't have duplicates.
So, it seems that eCS, using JFS or not, in a VBOX under Win 10 (or Linux) is not the problem. I need to ask if you updated everything after you installed, because some of the drivers in eCS 2.2 b2 do have problems (ACPI, AHCI, and USB, specifically). I am using the latest from Arca Noae, with good results. I also had one problem (a few years ago), where capping the processor at 50% allowed me to finish an install. After I got everything installed, I was able to put it back to 100%.
One other thing, that seems to make eCS (and WinXP) work better, in VBox, is to present the sound as a SoundBlaster 16. It seems to take a lot less processor power, the sound is good, and it doesn't break up.