What's the significance of my Player level?

Your Player level has two ramifications:

  1. Each increase unlocks more Permanent Upgrades.
    The number of upgrades per level starts at 1, increases to 2, then 3 and eventually settles at 4.
  2. It limits the max. level of your heroes - e.g. if your player level is 35, you can’t level up heroes beyond 35

Note: At higher levels the max number of permanent upgrades = 4 * Level - 34, but I don’t have a record of the number of permanent upgrades at lower levels, so would appreciate if someone can send me the data