Given that you do have general linux knowledge and rpi familiarity, here are my comments on your requests. I have 4 TX3 mini's three of which I run armbian on and one that I use the original android on.  I will mention that just because a box is labeled TX3 mini, doesn't mean the internals are the same.  The manufactures put identical external branding on boards that may be significantly different.  For example all TX3 minis claim they have emmc storage in them.  But only two of my TX3 mini