50 stocks is a lot to manage though. Are the results much different if you cut to 20 stocks, drop when out of 50?

Not difficult with an account at M1.com.
Set up a "pie" with 50 stocks ("slices").
Select all, and click "equal weight" and save.
Set up a portfolio that uses that pie.
Go to the portfolio and look at the buy & sell list, make sure it is as expected.
It will buy everything at the next trading window, usually the next morning.

When it comes time to rebalance, go to the pie, delete the ones that fell off the screen and add the ones that are new.
Select all, and click "equal weight" and save.
Go to the portfolio and look at the buy & sell list, make sure it is as expected.
It will sell & buy everything at the next trading window, usually the next morning.
Unless you tell the portfolio to do equal weight, it will only trade the ones that were added & deleted.

FWIW, I equal weight the pie but not the portfolio. That way it doesn't touch the stocks that are kept.