The Salamehfix works the same as external ilizarov, it's just more comfortable. It likely won't be noticeably easier because you still have metal going through your legs and have to deal with the same aches, pains, and possible complications that people who lengthen with Ilizarov frames have to deal with. How much you lengthen is more dependent on your own biology so if your soft tissues don't tolerate 7 cm well with Ilizarov then it still won't wearing the Salamehfix.
If it's about money there are some doctors in India with legitimately good credentials that are worth a visit.