I have an alternative idea. Bin it entirely.
You see, Fifth Edition back in 2014 had some OSR credibility. So lets do it the OSR way.
Encounter balance? Try to have approximately the same number of hit points and attacks per round on both sides for a fair fight. If one side has an advantage, it's an unfair fight. Roleplay accordingly.
And yes, that means 'run away or negotiate'.
As far as stats go... The Fifth Edition way of determining them is an arcane process of 'guess a Challenge Rating, work out the numbers, check if you were right, repeat if necessary'. That's not good design.
Instead, just use Hit Dice. It's what you do for player characters, after all. A 5 HD monster? It has a Proficiency Bonus of +3. Extending the Proficiency Bonus chart above 20 HD is easy... +1 every 4 HD.
I've done a few spot checks, and this actually doesn't have as big an effect as you'd expect. ±1 to attack rolls and saving throws, generally, with a lot of stuff unchanged.
The same rate of progression as an Old-School Thief or Cleric, in fact... Coincidence? I think not. Which incidentally means you can usefully OSRify Fifth Edition combat by dropping proficiency bonuses by 2 across the board, and losing the Constitution bonus to Hit Points.
This messes up the skill system, of course. That's the problem with unified resolution systems. Or just do ability checks, with advantage if the character has a relevant skill. That's a problem for another day.
Other than this, though....
* Encounter balance is a bit simpler
* Monsters are easier to build
* PCs are more less superheroic
Sounds like a good start, no?