What percentile for IV percentile is considered high and good enough to be considered for trading? Is there a thumb rule just as we have for probability OTM to be over 70%?

Typically in normal market conditions, you won't see many tickers above 50% IV Percentile. Although not a hard rule, anything above 10% IV Percentile is generally good for credit spreads! But of course, the higher the better.

That being said, just because a ticker has like 80% IV Percentile doesn't mean you MUST trade it. If another ticker has lower IV Percentile, say 40%, but it has much better liquidity, clearer trend, and you can collect more credit for it, then it's totally OK to trade the lower IV Percentile ticker. It's a multidimensional decision!