Is it better to have a Booster or Mimo Roof Antenna (the ones in the bundles)?

That's a tricky question as a roof antenna in the bundle supports MIMO which is typically faster than a cell booster that does not in 95% of situations. That said if you are in a 1 bar signal area a booster can give more benefit than a roof antenna. We travel with both but the booster isn't used 95% of the time or is only used to boost voice calls on our cell phones which is a nice side benefit. The roof antenna does provide a lot of additional cellular gain since it is on the roof and also has a 5db gain but the booster can do a lot more than that if pointed correctly. 

Adding a weBoost to this set up is possible, but it does require switching the antenna on the Pepwave from the roof mount cables to the stubby included ones.  Then having the interior weBoost antenna sitting next to the Pepwave.   Very possible, I have done this before, BUT? unless you are in the backcountry a lot, then a booster does really help that much.  They are great at taking ?just out of range coverage? and giving you a few bars of semi-usable internet, but if you already have service, boosters can slow the service down because they do not support MIMO or LTE-Advanced Technology which the modem does support.