Two shops in two states by one person

if aggregate turnover of both shop is less than 75 lakh than only he can opt composition scheme....means if both of his shop has turnover of 50 lakh each than his aggregate turnover is 1 crore, and hence he can't opt composition scheme.

for 2 different states then 2 different nos necessary

You can register as Regular Dealer. Then only you can transfer your goods to one branch to other branch (out side State)

Is it possible to register separately if we don't need to transfer goods between two states and turnover in total is less than 75 lakhs

Yes. Possible different registration for different states.
In my view, You have branches

In my view,
You have branches in different states, I think registration is mandatory....

yes....if turnover exceeds RS 20 lakh than you don't have any option but to take registration in all states where you have branches separately......if you take composition at one place than you have to take composition at all the places and by doing that you will be barred from making inter state sales or stock transfer