"How to record Profits/Losses"

Nothing about Loan Principal ever hits the P&L. The only Income would be interest Earned by the lender; the only Expense would be interest Paid by a business that Borrows funds to use for business purposes.

"from Loan Out S Corps, C Corps or LLCs in Personal books?"

Personal Books? The Person has debt. There is no expense write off for Personal Interest, and the Debt Principal is Liability, the same as their mortgage or their credit card balance or their vehicle loan balance.

"Should increase or decrease in Equity or Total Equity"

Equity is Net Assets; Assets = Liab + Equity, so being in debt Increases Liability and Decreases Equity. Paying down debt from Bank (asset) = Asset went down and Debt Liab balance went down. Equity is not changed.

"Net Income be reflected in Personal books?"

There is no Income from being in debt. Don't confuse Loan Proceeds and Income. Income is not the same as InFlow. Inflow comes from Sales, Wages earned, taking on debt, selling assets, etc. That is not Income, as a synonym.