Usually, you want CQB optics as far forward on the receiver as they can go. Reason is, it gives the best field of view (and as you say, with room behind for a magnifier). You don't generally want the optic on the handguard unless it is an extremely securely mounted free float (even then, it can mess with the weight balance).
Mount it as far forward as possible on the upper receiver. I have both my Aimpoint H1 and EOTech 512 mounted as far forward as possible on their respective guns as possible. As Technosavant said, it affords you the largest field of view.
It's personal preference, but my thinking is that a CQB optic isn't for precision, it's for fast target acquisition with both eyes open. Having it too far back, IMO, encourages you to try to use it as a magnified scope (one eye closed), and what you don't see CAN kill you.
But however you want to use it, it's your gun and you are the one who has to employ it, so do it in a way that YOU can make effective. Generally, though, the predominant thinking is exactly what I posted.
You can place the T1 or H1 from Aimpoint as far out as you like. Again, I have no personal experience with the EoTech. However, the 3x magnifier will require placement close to the eye, and that begins to dictate where you put the RDS. Check my photo above of the Bravo Company EAG Carbine with the H1 in front of the 3x magnifier. Those optics are where they have to be, give or take a slot on the rail.