First of all if you do a graft and to make it succesfull you should take a freshly cut branch cut it at a 45 degree angle and search a branch on your plant that’s the same thinkness and cut it basicly the same as your branch that you want to graft now place them nicely on eachother making sure that the cuts fit perfectly and now first take Some teflon to make the wrap and then tape it up you Will have a allmost 90-95% succes rate every time
As far as grafting sativa’s and indica’s it does not matter at all they just finish on your plant at different rates