If your major intercity travel is within a 7-day period, it's unlikely to be a good deal to get a 14-day pass just to have use of the pass on days when you're doing only short local trips.
The pass can be used for short local trips on JR lines, but the pass does not cover local subways or non-JR-train lines.
Do remember that the 7 day pass is for 7 consecutive days - not just any 7 days of travel in your 14 day trip.
For a Tokyo-Kyoto round trip, a 7-day JR Pass at JPY29K+ does not payoff. If you can return to Tokyo within 7 days, consider this e-voucher @JPY21K instead and you can ride on the most frequent Nozomi Shinkansen train.
use hyperdia.com to check train schedules, fares.
Even without the Japanican eVoucher the breakeven is not a Tokyo-Kyoto round trip as it only costs 26,160 yen (before using any pre-booking discounts), less than the 29,110 yen of the 7-day pass. Kyoto-Nara is 710 yen each way on JR so gtting close.
However, it is likely you will do 3,000 yen of other travel on JR trains in those seven days.