sativas generally do grow taller than indicas but both can get decent sized if they have a long growing season if planted in the spring they usually have months to veg before flowering in the fall so you should probably tie them down and train them if you want them to stay low to the ground seing how most strains are a cross between an indica and sativa even a mostly indica strain can be well over 6 ft if no training is done at all.
if you just recently started seeds they will not have as much veg time to grow as if you started in the spring so they probably wont get much taller as many have started to flower already.