Switching funds within your Roth IRA and Traditional IRA - provided you avoid "wash sales" with taxable accounts - would not impact taxes.
The differing opinions you read probably considered a mutual fund in a taxable account, where the sale could result in a profit or loss.
If you send money from your Traditional IRA to Roth IRA, that's taxable. You are "converting" money from pre-tax to after-tax, and that "Roth conversion" would be taxable.