[wrxtasy]

But how easy is dual boot controlled? Is so simple as with WeTek boxes?

WeTek hold down remote power button at boot time to flip flop between LibreELEC <<-->> Android. System remembers last selection.
Regular S905(x) dual boot. Boot into LibreELEC first - every time and select "Reboot to internal" from Kodi power menu for Android.

There is no "Reboot to internal" if you use any other Skin then the standard Kodi Krypton one.

Remove SD card with both systems - boot straight into internal Android.

In my case I need an Android Box with bluetooth capability for connection of BT gamepads for my young kids to play with Android games.
Also, If possible to install LibreElec and enjoy a nice platform for my movie database, while taking advantage of all Libreelec potential.

= AMLogic S905 / S905X box

Android games will run better on a NVIDIA Shield or AMLogic S912 systems due to superior GPU's in those boxes.

Apart from the nice MINIX U9 - AML S912 Marshmallow Firmware boxes are the worst Android / LE devices on the market.
AMLogic Nougat is better on cheap, Firmware unsupported devices.

No LibreELEC on Shield and problems with LE on the S912's.

I thought on buying 1 box AML S912 for my kids, and an Odroid for LibreElec. But, I couldn't reach a conclusion on what to buy. I made a list comprising Odroid C2 (or other if better), eMMc Android and controller, a power adapter and a case. An airmouse I would buy a Minix Neo A3 (or A2, depending on final budget). But, I'm not sure If this is sufficient.

I would strongly advise NOT to buy a MINIX A3 lite remote. There are a bunch of unhappy users on the MINIX forum complaining about MINIX A3 lite remote wake from sleep issues. (click). A2 is the preferred one.

Since, and unfortunately, I don't have a lot of spare time nowadays... to embrasse such project, I thought buying a "all-in-one" box that could not be "the best of the best" but at least would allow me to have android to play around with my family, and at the same time, have the possibility of doing a dual boot to LE.

Really for an all in one Plug n Play box you should be biting the bullet and buying a NVIDIA Shield. Dual boots are DIY and can be time consuming, so are researching, adding and configuring BT game controllers.

The MINIX U9 is also a decent Android device (A2 lite remote recommended) , with a strong GPU for games. Kodi Krypton on it runs pretty nicely indeed. Only real issue is rare H264 VC-1 video playback problems. There is also a pretty nice Android TV ROM available for it now as well.

I give a big importance to a good equipment to run libreElec, that's why I considered buying Odroid, but I also could't figure out the best online shop in Europe to safely buy.

Pollin in Germany stock ODROID gear.

https://www.pollin.de/

Be aware the ODROID C2 does NOT Dual boot. You have to physically swap SD / eMMC cards.

One big disadvantage of Mecool M8S Pro+, from my point of view, is that Bluetooth is unsupported.

Bluetooth may be supported via a cheap CSR v4.0 USB Dongle - the start of such added BT support is being tested now. Very early days tho.

So where does that leave you if you want cheap S905/S905X + Bluetooth with semi-decent Android, dual boot LibreELEC ?

Researching the Freaktab Website yourself for a S905(x) box with decent 3rd party Android ROM's.
It's why such devices are cheap and called DIY.

WeTek, MINIX, NVIDIA & Vero4K are more expensive because those devices actually come with seller Android / OSMC Firmware support. That ongoing support is built into the price of such devices.