JRphoto

Obviously the shutter speed dial should be set to anything else but Auto.
The command dial on the back of the camera becomes your aperture selector. The Auto position is reached by turning - not pressing - it to the right as far as necessary until the aperture number disappears. Confusingly you can turn it further to the right without anything further happening. Never mind, press the Menu button and verify that the title says Shutter Priority AE.
 
If you now turn the command dial to the left you activate aperture selection and enter manual mode. Again you may verify this by pressing the menu button and it will say Manual. The screen display will show both shutter speed and aperture.
 
If instead you turn the shutter speed dial to the Auto position you will enter Program mode (you can verify again with the menu button). In Program mode the display shows shutter speed and aperture. If ISO is set to Auto you can't change them, the camera will make the selection for you. If ISO is set to a fixed number however you can select another combination by turning (not pressing) the front dial. Combinations other than the one the camera would select are shown in yellow.
 
If you now turn the backdial to the left you will enter Aperture Priority mode. You can verify again by pressing the menu button.
 
I moved recently from X-M1 to X-T10. On the X-M1 there is a dedicated button position for each of these modes. On the X-T10 you have to memorise how to do it. It's not difficult but... The X-T10 is a much much more manually oriented camera than the X-M1.

What ??!! They stole my concept ??!!!!!!      

I've noticed interesting behavior in FW 4.20 , but I assume FW 4.21 has the same.
 
If you use Electronic Shutter then you can switch ISO dial to L / H1 / H2 and still shoot in RAW . It will just be recorded with ISO200 (it highlights that value with yellow).

Furthermore, RAW images canot be recorded setting ISO to L, H1 or H2 ( page 50, X-T1 manual).

I am shooting weddings with X-T1 and X100T and without issues. Yes, autofocus is slower but is more accurate then my previous Nikon cameras. For me DSLR is retro

I shot my first wedding with the X-T1 after having it for 5 days. Previously shot with a 1Dx, 2 5D3s and L glass. Sure there's a learning curve and a DSLR does some things better, but the X-T1 similarly has it's advantages. I've now sold all my Canon gear and have 4 X-T1s - I wouldn't go back. Anyone who says it's not suitable for pro wedding work is either ignorant or completely incapable of learning a new system. Here's a wedding shot 100% on Fuji, probably some of my best work. http://chasingsummerphoto.com/general/kirsty-and-tims-wedding-echidna-gully-armidale-wedding-photography-nsw/
 
Mirror less cameras are in their infancy, but are undoubtedly the cameras of the future. The DSLR will be dead in 10 years.

I can't say now how it worked in firmware 4.20 because I already "upgraded" to 4.21, but regarding this "Instant AF Setting in manual focus" issue, independently of what one sets in AE/AF-LOCK MODE menu item ("AE&AF ON WHEN PRESSING" or "AE&AF ON/OFF SWITCH"), it works in the same way, locking only when pressing, and unlocking after releasing the AF-L button,  as if this menu item was ever in "AE&AF ON WHEN PRESSING". At least mine is working in this way now.

If the lens don't have a clutch mecanism, setting the "M" mode (manual focus mode) in the X-T1 allows the use of the AF-L button to automatically focus (instant AF) AND lock the focus, but you still can use the focus ring to change the focus manually. It is more a way to instant AF in manual focus mode than to "lock" the focus. If the lens have a clutch mecanism, this procedure only works if the clutch mecanism is set in the AF position (the camera always in "M" mode); in this case, we only can focus using the AF-L button, and this is a very effective way of locking the focus because the focus ring can't move and the shutter don't focus in "M" mode. Hope this helps!

New Custom Display options of fw 4.20 allow to disable additional items in Custom Display mode.
 
also:
Focus Frame - it's useful to disable when you use Manual Focus lens.
Shooting Mode - Icon of "A"/"P"/"M"/"S"/"Multiexposure"/"Panorama" on bottom left corner
Information Background - is the transparent bar behind Shutter/Aperture/ISO (on LCD only).
Focus Mode - "MF" icon (only shows when M focus mode is set).
Shutter Type - "ES"/"M+E" icon on the right screen border
Continuous Mode - "BKT"/"CH"/"CL" icon (when corresponding mode selected on left top dial).
Dual IS mode - IS indicator icon
Movie Mode - Icon in right top corner
Blur Warning - Yellow icon in right screen area (it's often annoying while shoting portraits, glad it can be disabled now).

Nice hearing you! I made some loose measuments and the IR light remains lit about 20 minutes after turning the camera off (High performance ON). Well, maybe it is not even impacting in a sensible way the battery, but it looks like a BUG, and if it IS a bug, it is always desirable that Fuji fixes all discovered bugs. Maybe this is not a big deal, just a tiny bug, but I think Fuji will like to know and fix it. Cheers.