1. This depends on your intentions. As you know, a joint tenancy means whoever lives the longest ends up with 100% of the property. When one dies, the property does not go to the person's estate, it goes to the surviving owners. If you want the interest to be passed to the heirs of each owner, then a tenancy in common is the appropriate thing to do.
2. In a JT or TIC situation, each person owns 25% of the property. Nevada is a community property state, so if any spouse fell upon hard times, the other spouse would be drug along, exposing 50% of the property. Any creditor can only attach and liquidate what the debtor/debtors own. If one couple owns 50%, that's all the creditor could try to sell. If the property at issue is a house, it probably has little market value because the transaction would only be for 1/2 of the property. Having this set-up actually helps things from a risk standpoint.
2a. Because Nevada is a community property state, if one or both spouses file bankruptcy, the entire 50% would be exposed - but not the other couple's 1/2 interest. The trustee can attempt to sell 1/2 of the property. Again, if this is a residence, the trustee may not try to sell it because of its marketability. Who wants to own 1/2 of a house with a stranger!?!