I can guarantee you your BR2 is capable of carrier aggregation (CA.) This was true of modems used by Peplink loooong before the BR2. Even the older CAT6 BR1 Mini routers can do LTEA, for example.
Now, having said that, carriers handle CA differently. In the USA, for example, AT&T often does not invoke CA until it is needed. However, you’ll see it with T-Mobile right away.
As to the differences between the modems, I’ll let someone else respond. Meanwhile, I would not be concerned – the BR2 is an excellent device which should perform well for you. Congratulations on your ownership of it!
Both type numbers (Thales and Sierra Wireless) are based on Qualcomm x55 and do not have carrier aggregation for 5G (NSA and SA). They do support ENDC.
Any Qualcomm modem above x62 supports carrier aggregation.