Hi saviboy,
So this is true even regarding F speed? Airplane will slow to VAPP? and not stay at F speed?
As I understand it, Auto Thrust won't fly any slower than F speed if you leave the PERF MCDU set to CONF Full. However, since you've made a +ve correction to VAPP, then your new VAPP is usually > F speed so you won't notice the difference.
Will I even get GS mini in that case?
GS mini is active throughout the approach. See FCOM DSC-22_30-90 Speed Mode in Approach Phase.
I always reset the MCDU Landing CONF to 3 AFTER I'd applied the DELTA REF - just to keep it simple (for me).