Most transactions in a block

Block 689074 had 4,463 transactions.

  1. Is this the highest number of transactions in a block until now?
  2. What are the things that affect the number of transactions possible in a block?

Few observations based on comparison of two blocks (689074 and 666666):

Size of transactions:

size-of-tx

Type of transactions:

segwit-percent

Outputs:

outputs