If you are worried about buying the right policy for you, best thing to do would be to talk to an IFA or reputable broker. I have never heard of an insurance Co that doesn't implement Life claims promptly and since regulation changed (I think it ws 2017) compensation has to paid if they do not comply.
There can be delays if the pay out goes into the Estate and is held up by Probate. To avoid this the policy can be written in Trust and be paid straight out to your nominated beneficiary.
Another cause of delay woud be them having doubts about the validity of the claim. Say someone dies of lung cancer and have said they have never smoked, further enquiries may be requested.
Whatever you do when you decide, make sure you read all the terms and conditions.
Whole of life will be more expensive than Term insurance as it will definitely pay out because the inevitable will happen.