Yes, PIP/DLA continues after reaching retirement age, I was 66 last June and still receive PIP.
Pension credit is a top up to the state pension, to give you a minimum guaranteed income if you qualify for it.
As I’m disabled and also a carer I get an extra £416.92 added to my pension every month.
Information is here,
https://www.gov.uk/pension-credit-calculator
https://www.gov.uk/pension-credit
Sooner you apply the better, you can do it up to 4 months before you reach retirement age.
I sent an email to adviceline@carersuk.org listing what benefits I was receiving before reaching retirement age and they worked out what I would get.
Please excuse spelling/typos. Apart from being a clot it turns out I had one on my cerebellum that's now causing various problems!