voLTE is a feature driven by your network so if they support voLTE then yes it'll work.
Both sim slots do support 4G 》 well they did on my Note 9 so I shouldn't see why not on your model if it's a Dual Hybrid Duos version.
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.
Sim slot 1 is always the first one, and sim slot 2 is always the one where micro SD can go into?
Can both sim cards use 4G and VoLTE?
Did you put in 2 sim cards to see for yourself?
The answer btw which can easily be found is a resounding Yes.
VoLTE is carrier based as it has been since its rollout