Benefit life assurance registered vs non registered confused

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I've moved jobs and I get life assurance at 7 x salary I can increase this if I want (at my cost) which I did in old job. I want to increase to x10 but its asking me for a split between 'registered' and 'non registered' scheme. I read up on the difference and to me basically it seems registered scheme any thing above life time allowance is taxed and in unregistered above life time allowance no taxed and premiums for scheme handled differently.

If I died today the total of my pension and work life assurance payout would just take me above the life time allowance, so I guess that means if I increased it to 10 x my salary the additional 3 x I should have in unregistered scheme?

Im confused as well as my old job I was not asked the question about reg vs non-reg but was told life assurance will be tax free it I died. My new job they seem to default me into registered and then I can pick unregistered for extra but I guess as my pension funds increase ideally I should have more multiples in unregistered? Is there a specfic legal requirement you must meet to have all unregistered?

Thanks