Why blind selection?
Strongest one will be selected.
Even if threshold is defined, and all the beams are weaker than threshold, then also strongest beam is selected.
NSA or SA this parameter can be there if configured.
3GPP TS 38.321 5.1.2 Random Access Resource selection
1> else (i.e. for the contention-based Random Access preamble selection):
2> if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB is available:
3> select an SSB with SS-RSRP above rsrp-ThresholdSSB.
2> else:
3> select any SSB.
Yes beam level result there, but we consider generally cell level results which is linear average of SSB beam exceeding SSB threshold defined under meas object.
So let’s say UE latched over SSB beam index 1 on cell 1 after handover move to which SSB beam index on cell 2.
It’s not defined
But as you mentioned, after HO UE will select new beam index on the basis of SSB RSRP threshold, so it’s ok.