Don't forget that with Option 1, you can sell the apartment buy a new house and move the tracker to the new house. You will pay an additional 1.25% on the tracker element.
So, if you are paying ECB + 0.75% now, you will be paying ECB +2% on the new mortgage.
That is usually the best option.
But if you want views on whether or not to keep the property as an investment, you would need to give a lot more information
Amount of mortgage
Rate
Value of property
Potential rent and expenses.
Your income
Your savings
The price of the new house.
Brendan