actually
maximum weight is 4mb but there is a secondary limit of maximum weight / witness scalefactor(4)
meaning there is a limit within the code of 1mb

this 1mb limit is a pre-requisite for transactions
it is where legacy transactions have been restricted to only be within.
and segwit transactions are semi restricted to being within.

segwit transactions do not get full free reign of 4mb. part of a segwit transaction is restricted to the 1mb limit
its only the signatures of a segwit transaction that get to sit outside the 1mb limit
so an average segwit transaction where signatures = half the data of a transaction would result in ~2mb blocks
but this is in a usecase of if every transaction in the 1mb base limit was segwit and where half the transaction data was its signature
EG
if the majority of transactions were legacy then only a few segwits would have their signatures outside the 1mb area
meaning expect less than 2x

so dont expect transactions to fill up the 4mb weight as a 'norm' .. as the 1mb area is still a pre-requisite and restricts full utility.