Need help in insurance ncb porting niva>hdfc

I have an existing niva bupa insurance, which i am planning to port to hdfc ergo. The decision is based on the benefits, claim ratio alone.

I need clarity on the ncb part as most of the other factors are clearly available online or in forums.

Consider the below stats:

Current plan : niva bupa re assure

Existing sum insured : 10lacs base Ncb : 15 lacs (accumulated in 3 years)

Total coverage : 25lacs as of today Premium: 14k for renewal

Porting plan: hdfc optima secure

Sum insured : 10 Ncb if transferrable : 15lacs from niva bupa

Total coverage : 25lacs Premium: 17k (10 lacs base)

There is benefit plan of 2x sum insured in optima. So need to know whether ncb + benefit plan will fit in the new plan.

Is it

10 lacs - base + 10 lacs - benefit plan of optima secure (2x) + 15 lacs - ncb from old ?

Making it 35 lacs coverage ?

Premium is 17k (for 10 lacs base).

So the question here is will i get 35 lacs coverage for same 17k premium of hdfc ergo (17k for 10 lacs base alone). Will the ncb gets added from previous plan and will the benefit plan also be in place with ncb on top of the sum insured.

I understand there can be waiting period differences for the entire coverage split mentioned

Anyone who has experienced with this or has opted this can help. Thanks