dilseaniket
Hi
T4 framework is our all new framework based on the latest technology with new features. All the new template we are making is based on T4 now. T3 is our previous framework used for years, so there are more no. of template with that. But now you will see all the template released are T4.
You can use the Builder or any template but if you are choosing T4, there is less chances of conflict as both are based on same framework.
If you are thinking T4 has less templates compare to T3, Its just because T4 is new , after an year you will see more template no. increased. As all new JA templates based on T4.
dilseaniket (I think both bootstrap versions are different)
Yes T3 is based on Bootstrap3 and T4 is on Boostrap 4, as Bootstrap 4 is latest framework at the moment.
Let me know if there is any doubt or question on this.