The excluded tax amount will be each time the same, example: excluded tax amount is 100$, And the taxes will be calculated ere the payments during the checkout and added to the excluded tax price depending on your client evidence, your tax threshold, and the quality of the item sold. If selling tax/VAT/GST is due, calculated, and add it on top of the 100$. example: Italian customers: VAT is 22%. the calculation is 100$ × 1,22 = 122$, this amount is the price in which you will sell your service/product.
A Tax Included means that you sell a service or product at a similar price for all buyers at all times in all countries. For example, if you market an object for 100€ in your country, it will be sell for the same price in all countries. And the tax calculated after the amount depending on your customer evidence, your tax threshold. If sales tax/VAT/GST is due, will deduct the tax amount from the 100€ you sold.
Calculation when the price is inclusive : Tax amount = Value inclusive of tax (Amount) × tax rate ÷ (100 + tax rate)