Which of the 4x12 Mesa cabs with MkIIB+ Combo?

I’d appreciate opinions as to which of these two cabs would be preferable for my current equipment and style. Both are the same $. My iib+ combo is sixty watt with EV speaker, reverb, and GEQ. I use a lot of different tones, from jazz clean to metal scream, both with and without pedals. My initial thought is the semi-open back cab for more open highs when clean. However, I’ve never been a 4x12 player, so this is new territory. Also, I’m not sure about their impedance, but assuming 8 or 16ohm, could I use it in combination with EV combo speaker? Standard boogie 4ohm minimum speaker outs.

Here are the details:

“Mesa Boogie Vintage Full Stack - Top cab is 4 x 12's open back top with Celestians G12H-100's with EV's in the bottom. Bottom cab is 4 x 12's EV's”

You asking about using two 4x12 cabs with your combo?
Asking as you've posted speaker specs about a 4x12 "Full Stack" which is using both a top and a bottom 4x12.

Fwiw both 4x12's are likely wired in series-parallel with all 4 speaker being 8ohms each.
The end result is an 8 ohm cab.

If you use one of the cabs with your EV loaded combo, then yes, the use two 4ohm speaker jacks on the back of your combo.
If you want to use both 4x12's then disconnect the speaker in your combo and plug both of the 4x12 cabs into the 4ohm speaker jacks.

Your 60 watt IIB with the EV loaded combo is already giving you the open highs when clean.
Not sure why you think a 4x12 is going to change that/ give you more open highs
(other than what the 4x12 with the Celestion G12H-100's up top will give you versus the 4x12 with EV's up top).